Note: Descriptions are shown in the official language in which they were submitted.
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81099-BKR
--1--
BIDIRECTIONAL, INTERACTIVE FIRE DETECTION SYSTEM
Background of the Invention
Various detectors and systems have been de~ieloped
~o detect and indicate the presence of particles
of combustion, or of a fire, or of an increase in
temperature. Such systems generally use two or more
conductors between a control panel or control unit,
which is coupled to the individual detectors. In
general, the individual detectors determine when an
undesired condition is present, by comparing some
parameter (such as current flow or voltage level) with
a predetermined reference value. When the detector
determines the reference value has been exceeded, the
undesired condition is present and the detector
latches in the alarm condition. Generally the control
unit does not know the precise location of the alarmed
detector, and a ter three or more detectors have gone
into alarm on one zone, cannot recognize how many
detectors are in the alarmed condition on that zone~
Prior art detectors generally are not capable of
having their sensitivity checked from the control
panel over a two-wire loop, or having their sensitiv-
ity adjusted ~rom the control panel without taking the
system out of operation.
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810 99--BKR
A serious shortcoming of prior art systems is
that loop continuity is supervised, bu~ detector
presence and/or operation is not supervised. If any
detector is removed and replaced by a cardboard form
or some other mechanical unit to simulate detector
presence, continuity along the conductor pair is
maintained and the control unit does not "know" that
the detector is in fact missing from the area.
Several of these shortcomings are overcome in the
system of this invention which includes a bidirectional,
interactive fire detection system in which only a
single conductor pair is required. The control panel
(or controller) selectively addresses the individual
transponders, and each transponder responds when
addressed. The controller also issues command signals
to the addressed transponder, which command signals
represent desired functions or actions to be taken by
the selectively addressed transponder, which then
accomplishes the functions or actions. Such command
signals can con~rol the operation of various devices
coupled to the transponder, such as relays, visual
and/or audible indicators~ or any other device.
In the system of this invention the transponder
returns a signal which identifies the type of transducer
associated with that transponder. For example, the
transducer could be an ionization detector, a photo-
electric detector, alarm-causing switches (such as a
manual pull station or a thermal switch), non-alarm-causing
switches (such as an abort control for Halon, or
day-night switches) or a complete zone of detectors
This return signal is termed the "identification
response".
81099-BKR
The transducer also returns a "transducer response",
a signal from which the controller determines the
transducer sensitivity. Successive transducer response
signals can be recorded to provide a continuing record
of transducer sensitivity, as described in the earlier
application. In the system of this invention, it
is desirable to compensate for changes in the transducer
response signal~
Even with the significant improvements just
described~ there are areas in which such a bidirectional,
interactive system can be further improved. It is
highly desirable that the transponder return a reference
signal from which the controller can determine that
the transponder is functioning properly. This signal
will be referred to as the "calibration response". In
addition, it is dèsirable khat the system be equipped
to compensate for changes in the calibration response
signal, and further that at least certain transducers
be capable of selective and remote calibration.
Also very ~mportant is that the transponder return
signal, the l'transducer response" from which the con-
troller determines the transducer sensitivity, be used
in a manner to provide adjustable sensitivity of the
transducer.
Anokher important consideration is that the
improved system be useful to control a multi-zone
system.
In addition, where a plurality of zones are
coupled to the same two common terminals, it is
desirable to identify the separate zones one from
another. The "identification response" signal ~an be
7~67~
81039--BKR
--4--
used to provide this identification of the individual
zones.
Another significant consideration is that the
controller of the system should be able to "read
through a short", that is, discern usable and significant
information whe:n a transponder is replying over the
conductor pair, even though one or more additional
transponders may inadvertently have its output fail
in an open or shorted state when the addressed transponder
10 iS replyinq.
Yet another important consideration is that the
system be a~le to poll the transponders at a time
when the controlled premises are substantially un-
occupied and quiescent (for example, 2:00 a.m. Sunday),
to obtain and/or store various reference data.
Another desira~le advantage of the improved
system is that it be able to identify the precise
location of a break in one wire of the conductor pair.
Another important consideration of the improved
system is that ;t be able to measure the analog
representation of the signal returned from the trans-
ponder with a greater accuracy than would be possible
with a simple, coarse measuring arrangement, without
imposing the requirement of greater accuracy on the
system over the entire information-return time interval.
Yet another important consideration is that th~
new system be capable of providing a compensation
signal to the controller as a function of various
conditions, such as component aging, wind velocity,
temperature, humidity, supply voltage at the associated
transducer, and so forthO
A ~idirectional, interactive system for detectiny
and indicating a predetermined condition, such as the
81 099-BKR ~7~6~3
presence of fire or products of combustion, when
constructed according to the teaching of this earlier
invention, need employ only two conductors. A controller
and a plurality of transponders are each coupled to the
same conductor pair, without any need for an end-of-line
resistor or other termination unit,~or without any
other means for supplying power to the transponders
and/or transducers~ The controller sends out a series
of signal groups or sets, with each signal group
addressing a paricular transponder. One or more of
the signals in a given group can be modified by
the controller to pass information to the addressed
transponder. Each transponder has a unique address
and, when it recognizes its own address, can return
information to the controller by modifying some
characteristic of one signal directed back to the
controller. It is important that each transponder
does not depend on the proper operation of the other
transponders for receiving or sending information.
Each transponder can return information concerning the
identification and condition of associated transducers.
Particularly in accordance with the present
invention, the controller includes means for operating
upon a transponder-response signal to derive an "answer"
siynal. The answer signal is a function of both the
time duration and the amplitude of the transponder-response
signal. The answer signal is then examined to determine
whether a particular transducer has returned a signal
implying alarmf trouble, or some other condition. The
sensitivity level -- or alarm threshold -- can be simply
adjusted in the controller. In addition the answer signal
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provides the desired calibration response from the
transponder, in answer to the appropriate command from
the controllerO The system compensates for changes in
the calibration response as well as in the transducer
response, and allows the individual transducers to be
selectively and remotely calibrated, in real time, without
affecting system operation during the calibration interval.
The answer signal is provided from each zone in a
multi-zone sys-tem, and thereafter processed to provide the
lQ desired information (such as alarm, trouble, "read through
a short" (where a "short" means a shorted output driver),
or whatever is desired). The "reading-through-a-short"
capability is included in the amplitude-responsive portion
of the circuitry which produces the answer signal.
Specifically, the invention relates to a fire
detection system comprising a pair of electrical conductors,
a controller connected to transmit data over the electrical
conductors, a plurality of transponders coupled to the
conductors for returning data to the controller~ and a
transducer coupled to one of the transponders. The
transponder includes means for returning the data as a
function of the transducer response. The controller
includes means Eor storing a limit signal, means for
receiving a data signal denoting transducer response from
the transponder, and is characteri~ed by means connected to
compare the received data signal against the stored limit
signal, to provide a transducer sensitivity signal as
represented by the difference between the stored limit
signal for the particular transducer and the transducer
response information provided by the received data signal.
In accordance with an important aspect o~ the
invention, the "answer" signal is derived by using
both vernier and coarse mea-suring circuits during the
response period, with the vernier or fine counting
only used for a portion of this response interval to
enhance the accuracy of the answer signal.
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In addition, the system provides a compensation
signal which can modify the processed information as
a function of different variables, such as changes in
wind velocity, temperature, humidity, supply voltage
to a transducer coupled to a transponder, and so forth.
The Drawings
In the several figures of the drawings, like
reference numerals identify like components, and in
those drawings:
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7~67~3
81099-BKR
FIGURE 1 is a block diagram of a prior art fire
detection system;
FIGURE 2 is a block diagram of a fire detection
and signalling system constructed in accordance with
the principles of the inventive system;
FIGURE 3 is a simplified schematic illustration
of the controller and one transponder of the system
of this invention;
FIGURES 4 and 5 are graphica1 illustrations
useful in understanding operation of the system of
the present invention;
FIGURES 6A, 6B and 6C are graphical illustrations,
taken on a scale enlarged relative to that of FIGURES
4 and 5, useful in understanding operation of the
lS present invention;
FIGURE 7 is a functional block diagram o a
transponder useful with this invention;
FIGURE 8 is a schematic diagram of a transponder
used with the present invention;
FIGURE 9 is a functional block diagram of an
integrated circuit useful in the transponder shown in
FIG. 8;
FIGURES 10 11 and 12 are graphical illustrations
useful in understanding how the present invention
derives information contained in a parameter of a
signal;
FIGURES 13, 14 and 15 are block diagrams of one
: system for implementing the present invention;
81099-BKR
~8~
FIGURE 16 is a schematie diagram of a Class A
arrangement, useful in understanding eertain advanta~es
of this invention;
F~GURE 17 is a block diagram useul in understanding
the signal--processing in the present invention; and
FIGURES 18, l9A-19F, and 20A~20F are graphical
illustrations useful in understanding the invention.
Detailed Description of the Invention
FIG. 1 depicts a known arrangement of a plurality
of detectors 20 coupled between a pair of conductors
21, 22. A control panel 23 is coupled to the conduetor
pair for supervising the loop, and an end-of-line
device 24 is connected across the conductor pair to
provide a termination. This affords continuity of
current flow along the lines. In sueh arrangement the
actual detection is aecomplished by one of the deteetors
sensing the fire or presence of particulate matter,
going into alarm and providing a ehange in voltage or
eurrent on the conductor pair which is detected at the
control panel. With such an arrangement it is not
possible to determine the exact location o the alarm
condition, but only the loop (completed by conductors
21, 22) on whieh the alarm condition has occurred.
FIG. 2 shows a plurality of transponders 25
rather than simple detectors, conneeted to operate in
conjunction with a controller 26, coupled to the same
conduetor pair 27, 28 to which the transponders are
eonneeted. The term "transponder" as used herein ~nd
in the appended elaims signifies a unit which can eontrol -
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81093-BKR
_g_
and/or monitor some condi.tion and/or as.sociated component
which may or may not be adjacent its physi.cal location,
is selectively addressed by the controller and recognizes
not only- its address but additionally o~her information
which may be transmitted from the controller, such as
command signals for controlling the operation o the
transponder itself and/or various assoc;ated devices.
In addition ~he transponder i~self transmits information,
such as the transducer response and ident;fication
response, back to the controller. Thus, the trans-
ponders 25 truly interact with. the controller to provide
a ~idirectional r interactive system. Each transponder
is not a passive device which merely transmits some
signal when activated by a master transmitter. It is
also emphasized that there are no terminations at the
end of the conductor pair 27, 28, or on either of the
other pairs 31, 3~ and 33, 34 which branch off ~rom
t~e main pair 27, 28 in zone 2. It will become
apparent that such branching is possible without
2Q regard either to physical location or to the order
i.n which each tranæponder is addressed. Such an
arrangement, with no requirement for termination at
the end o any conductor pair, provides a system
which.is simple and economical to install and operate.
FIG. 3 depicts in simplified form the manner in
which interactive signalling is accomplished between
controller 2~ and one of the transponders 250 As
there shown, controller 26 operates with a reference
voltage V applied bet~een conductors 35, 36. Conductor
35 is coupled through a resi~tor Rl to conductor 37,
which is connected over a connecting screw 38 to
conductor 27. Conductor 3~ in the controller i5
connected over a screw 40 to line conductor 28. In
the controller a switch Sl is coupled in parallel
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81099-BKR
-10-
with a resistor R1. Another resistor R2, is con-
nected between conductors 37 and 36. A sensing
conductor 41 has one end connected between resistor
R2 and conductor 37, to provide an indication of the
voltage across resistor R2.
In the transponder, a resistor R3 has one end
coupled to conductor 27~ and its other end coupled
through another switch S2 to conductor 28. In this
preferred embodiment all of resistors R1, R2 and R3
are the same resistance value. However, those skilled
in the art will appreciate other values and/or ratios
can be selected without departing from the principles
of this invention. A command circuit 42 regulates
the opening and closing of switch S1, and other
components in transponder 25 (not shown) regulate the
open and closed times of S2. The remaining components
depicted in FIGo 3 will be described hereinafter.
The interactive communication is accomplished
with the modification of at least one characteristic,
such as voltage amplitude or the time duration of a
signal, or the modulation of more than one such
characteristic, such as both time and amplitude.
The amplitude of the voltage used in signalling is
simply controlled by switches S1 and S2. Switch S1
is closed to "send" each signal or pulse in each
signal group of pulses from the controller over the
conductor pair 27, 28. With switch S1 closed,~ a
voltage of amplitude V is passed over conductors
27, 28 to all the transponders. The duration of
switch closure can also be recognized at the trans-
ponder, as can the number of times switch S1 is
opened and closed in each group of signals or pulses.
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7~36~13
81099-BKR
In the case where Rl, R2 an~ R3 are of equal
resistance, and with switch S1 open and switch S2
opPn, the voltage on sense conductor 41 is V/2,
determined by the resistance bridge including resistances
Rl and R2. Thus when transponder 25 is answering
back to the controller, a voltage V/2 received on
sense conductor 41 signifies switch S2 is open. When
S2 is closed, while Sl remains open, this places R3
in parallel with R2, and this parallel combination is
in series with Rl to determine the voltage at conductor
41. Thus with switch S2 closed, sense conductor 41
"sees" a voltage level of V/3 returned to thP controller.
Additionally the number of switch openings and closings
are also readily determin~d in the controller.
Closure time of S2, while Sl remains open, can
be made a function of a signal developed by an associated
transducer (not shown~ r or can be made a unction of
any desired information-bearing signal. By measuring
the time duration of the S2 closure time, the information
represented by the original signal can be determined.
Closure time of Sl can be regulated to control issuance
of command signals from the controller to ~he trans-
ponders.
Controller 26 derives information from the
transponder replying by measuring ~he time duration
of S2 closure, or time duration of voltage ~/3 appearing
across R2. An important aspect of the invention i5
that significant information can still be derived by
the controller, when one or more additional trans-
ponders are replying concomitantly with the a~dress~d
~ransponder. To this end it is important that con~roller
26 be able to discern when --- and how much --- the
voltage on sense conductor 41 falls below V/3. Ac-
cordingly, ~ontroller 26 includes a signal examining
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81099-BK~
-12-
circuit 43 to make thls determination. In examining
circuit 43 is a voltage divider circuLt 44, including
four resistors 45, 46, 47 and 48 connected in series
between a source of unidirectional voltage and ground.
An array 50 of comparatoxs 51, 52, and 53 is provided
and connected as shown, with. one input of eac~ com-
parator coupled to sense conductor 41 and the other
input coupled to a connection in voltage divider
circuit 44. Comparator 51 is connected to provide an
output signal on conductor 54 when the signal on sense
conductor 41 is V~3 or less (plus or minus a suitable
tolerance~. This signifies ~t least one transponder
is replying by closing its switch S2. In accordance
with an important aspect of the invention, comparator
52 is connected to provide an output signal on conductor
55 when the signal on sense conductor 41 is V/4 or less
(again, plus or minus an appropriate tolerance value).
Such an output signal indicates two or more transponders
are replying, each closing its switch S2 and placing
its respective resistor R3 in parallel with R20 By
making a logical comparison of the output signals on
lines 54 and 55 at any given instant, the presence of
a signal on line 54 with no signal on line 55 indicates
that one, and only one, transponder is then replying
over the lines 27, 28. Also important is the connection
of comparator 53 to provide an output signal over
line 56 to command circuit 42 whenever the amplitude
of the signal on sense conductor 41 is at a level of
V/5, or less. This denotes three or more trans-
ponders are replying, or t~ere is a short across lineconductors 27, 28. Under such. conditions the output
signal on line 56 is used to shut down command circuit
17867
81099-BRR
-13-
42 and indicate the trouble condition. By making a
logical comparison between the presence of a signal
on line 55, from comparator 52, and a determination
that the command circuit 42 has not been shut down,
it is possible to determine that two transponders are
responding ~signal on line 55) and also that a third
transponder is not responding at this time, ~ecause
such a condition (third transponder replying) would
have been indicated by a signal returned over line 56
to shut down command circuit 42.
Those skilled in the art will appreciate that the
number of comparators 'n' in examining circuit 43 of
FIG. 3 (where in the illustrated embodiment n = 3),
n-l number of transponders replying may be specifically
identified, while n or more txansponders replying, or
a short across conductors 27 and 28, is considered an
unacceptable operating condition, which is identified
by a signal on line 56 out of comparator 53.
To ~ettar understand the system operation, a
description of ~he signal groups transmitted from the
controller and returned by the transponder will be
helpful. FIG. 4 indicates a series of signal groups
for sequential passage over line conductors 27, 28 to
the different transponders connected across these
conductors. Each signal group such as the group
shown under the legend 'Itransponder 1", includes the
same number of pulses. In a preferred embodiment
four pulses were used in each group for one transponder
address, but those skilled in the art will appreciate
that a different number of pulses can ~e utilized.
The extended pulse at the high amplitude le~el shown
under "address 31" and the first portion of "addxess
0" indicates a reset action, and is also used to
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81099-BKR
-14-
charge up a component in the transponder to provide
energization of that transponder throughout the
polling cycle. As will become apparent, each transponder
includes a counter circuit to acc~mulate the number
of pulse groUps sent over ~he line conductors, and
thus recognize when its address is indicated ~y the
controller. All the high level pulses ~after address 0)
shown in FIG. 4 are of short duration, signifying
that no command signal was sent by the controller but
only different addresses, as indicated ~y the number
of pulse groups.
FIG. 5 illustrates the manner in which one
pulse group is modified to pass a command signal to a
particular transponder. As there shown, when the
seventeenth transponder is ~eing signaled, the second
pulse in the group has its high level portion extended
for a considerable time, which may be 40 milliseconds.
The precise time is not critical, because each transponder
can include a simple timer to determine when the
pulse amplitude has remained high for a minimum time,
represented in FIG. 5 ~y the distance between to and
tl. This time was about 20 milliseconds in the
preferred embodiment, representing a "wait" period.
Because the transponder recognizes that this is the
second incoming pulse, it knows the action to be
taken if the pulse high is stretch beyond the "wait"
time tl. Suppose the elongation of the second pulse
denotes a command to turn on a light-emitting diode
(LED), or other suitable Yisual indicator. As soon as the
pulse high extends heyond tl, the LED is turned on
and it remains on until time t2. T~e transponder can
recei~e different command signals as different high
level pulses in the group are "stretched" to various
lengths. Those skilled in the art will appr ciate that
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81099-BKR
-15-
the controller may vary the duration of the S1
closure, and thus the duration of the high level
pulses (such as the pulse between to and t2, thereby
encoding information in addition to that shown in the
illustrated embodiment, and thus the flexibility of
the system is substantial. It is important to note
that after the wait period, the appropriate component
(LED), relay or other unit) is energized while the
pulse is still high. This means the energy for the
component is supplied from the controller over lines
27, 28, rather than being supplied by the transponder~
This will be explained more fully hereinafterO In a
similar manner the transponder returns information by
closing its switch S2 and thus providing a data return
signal at amplitudé V/3, analogous to an extended
closure of switch S2 in FIG. 3. This will be explained
in more detail in connection with FIGURES 6A, 6B and
5C.
FIGURES 6A, 6B and 6C are helpful to understand
the transmission of data from any of the transponders
25 to the controller 26. This is accomplished with
the switch S1 of the controller in the open position,
and switch S2 in the transponder is selectively
closed to transmit the data. With each closure of
switch S2, the voltage on sense line 41 o the control-
- ler goes to V/3. The length of time that the voltage
on conductor 41 remains at V~3 is a function of the
controller (time duration o~ S1 open), and also the
transponder ~time duration of S2 closure). The S2
closure time in turn depends upon some characteristic
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81099~KR
--16--
(such as voltage amplitude~ of a detector or any
other transducer associated with the transponder, or
of information generated within the transponder
circuit. Such associated detector ~or transducer~,
or internal information generation, will ~e explained
hereinafter.
FIG. 6A depicts one of the pulse groups, such as
those in FIG. 4 under t~e legends "transponder 1" and
"transponder 2", taken on a scale enlarged relative
to that of FIG~ 4. In FIG. 6A the four pulses have
"lowsl', or the low-amplitude portion of each pulse,
designated 141, 142, 143 and 1440 The fourth low 144
occurs in the time duration referenced 145, and, in
this embodiment, this duration is itself subdivided
into three "windows" or time intervals 146, 147 and
148. It is manifest that any d sired number of windows
or time intervals can be provided, depending on the
degree of accuracy required. There is a transition
150 in the fourth iow, which as shown occurs in the
center of window 147. This transition is within the
"normalll window 147, and indicates llnormalll aperation
of the component under discussion (whether an as-
sociated transducer or a component internal to the
transponder) providing the inormation for return in
the interval 145. By way of example, this could
signal the normal condition of an associated detector,
or the open condition of an associated switcho If the
transition occurred in the initial part of the interval
145, within time window 146, this is a low~voltage
indication and could be used to indicate a txouble
condition o an associated detector, or t~at a switch
is not connected. If the transition ccurs wit~;n
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81099-BKR
window 148, toward the end of time duration 145, this
could be a signal, by way of example, that the as-
sociated detector is in an alarm condition, or an
associated switch is in the closed position. It is
emphasized that the time duration of t~e initial
portion of the pulse low, ~efore the transition, is
made to represent the voltage amplitude at t~e trans
ponder. Of course, t~is time duration could be made a
function of other parameters, such as frequency or
current level. In addition, transducers other than
smoke detectors or switches can provide condition-
indicating responses within time frame 145. For
example, if a temperature-indicating transducer were
connected to the transponder, a transition within
window 146 could indicate a low temperature, a transi-
tion within time interval 147 could signal a medium
or normal temperature, and a transition within window
148 could mean a high temperature. While the transition 150
has been emphasized in the general description of FIG.
6A, it will become apparent that the time measuring
scheme of the invention does not look fox the transition,
as such. Rather the system continually examines, at
predetermined intervals such as one millisecond, the
level of the voltage during interval 145, and ac
cumulates a count related to the time that the signal
is at V~3 durin~ time interval 145. This provides a
substantial improvement in noise immunity and measure-
ment accuracy, as will be explained b~low. With the
simple s~stem and respon~e indications shown in FI5.
6A, those skilled in the art will appreciate the many
modîfications that can ~e made in this flexi~le
system.
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81099-BKR
-18-
The interval 145 wa~ "stretched" or elongated by
51 remaining open to provide an adequate time duration
for signifying the amplitude of a related analog
voltaye level. Of course, any of the other pulse lows
141, 142 or 143 could have been elongated to send back
information, ~ut if elongated, the data transmitted
would have ~een different. In the illustrated em~odiment,
stretching or elongating the first pulse 141 permits
the transponder to transmit its cali~ration information
in its entirety, based on a xeference voltage. Stretching
of the second low 142 permîts the transponder to
provide information identifying the transducer or
other component associated with the transponder.
Stretching either of the lows 143 or 144 permits the
transponder to return information concerning an analog
signal supplied to the transducer. In the example,
only one pulse low was stretched, but more than one
pulse low~can ~e elongated in a single return. Alternatively,
no pulse low will be stretched if no information is
desired to be returned. Thus there can be 0, 1, 2, 3,
or 4 pulse lows stretched in any single group of
pulses, in the embodiment where 4 pulses are used fox
one transponder address.
Because the first two pulse lows 141, 142 extend
~elow line 43Q but short of line 431, the controll~r
is able to determine (~y examining the voltage level
on sense conductor 41~ that the transpondex switch
S2 was closed. The switch closure establishes the
voltage level V/3 on the sense conductor 41, and that
level is within the amplitude range defined between
lines 43Q and 431. At the time the third pulse 143
would ~e transmitted from the transponder, with no
associated transducer or a zero signal level at that
transponder, its switch S2 is not closed. ~t this time
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81099-BXR
--19--
the voltage on the sense conductor i5 Y/2, determined
by Rl and R2, and representea by lo~ 143 in FIG. 6A.
This response at level V/Z does provide infoxmation,
namely there are no S2 closures --- in the addressed
transponder or in any other ~ransponder -- at this
time.
If an ionization type smoke detector were
connected to the responding transponder, ~he "stretched"
pulse lsw in time interval 145 can convey information
as follows. The entire time interval might have a
d~ration of 32 milliseconds (ms)~ to denote a voltage
amplitude range of 0 to 8 volts. Thus each millisecond
of pulse duration represents 0~25 volt~ In this
em~odiment the first or trouble window extends l~
ms, representing 3 volts; normal window 147 is of 8
2Q ms duration, denoting ~ volts; and the third, or
alarm, window lasts for 12 ms, indicating 3 volts.
Thus with the transition 150 occuring as shown, the
transponder is "telling" the controller that a
voltage level of 4.0 volts has been connected to the
appropriate input of the transponder from thei
associated transducer, in this case an ionization-
type smoke detector. The controller then operates
upon this voltage level to determine how far this
~oltage (4.0 volts) is ~rom a reference level for
that specific transducer to determine the state of
that transducer. In addition this measured voltage
level may be compared with a previously recorded
voltage level from the same transducer. When the
previous voltage level was recorded prior to a
relatively long time period, say a week or more, the
comparison can provide an indication of gradual
~ ~ i
.
' ' . : ' ' `
~7~7~
81099-BKR
-20-
changes in the detector operation/ which might be
caused ~y component aging or dust acc~nulation.
By noting the extent of the change in detector
operation, the change can be compensated in the
system and thus avoid an erroneous indication of
alarm or other condition. In addition the extent of
the change caused by dust or aging can be utilized
to indicate that maintenance is needed (cleaning
and/or other repair of the system), to avoid an
unwanted alarm or trou~le condition. By compensating
for the long term changes in the detector voltaye,
the controller is continually able to determine the
true sensitivity, or "distance" from alarm, of each
detector. This is an important advantage over the
earlier described system, and over prior art systems.
In this embodiment only three windows or measuring
intervals are used, to simplify the ~xplanation. If
the transition 150 had occurred in the window 146,
this is in the time range of 0 to 12 ms and represents
a voltage amplitude of 0 to 3 volts at the detector~
A transition in this range signifies there is some
trouble condition, such as an open circuit at khe
connected transducer, or a circuit malfunction in
the transducer. If the transition occurs in the
third window 148, this signifies a voltage in the
range of 5 to 8 volts within the time duration of
from 20 to 32 milliseconds. A transition occurring
during this time frame indicates the connected
transducer is in the alarmed state, when this signal
3a is processed at the controller. That is, the con-
troller compares thR returned signal to the previously
stored alarm threshold reference level, and when it
determines the return signal i5 a~ove this level,
, 1.
' ~17~78
81099--BKR
-21~
the alarm condition is indicated by the controller.
It is thus apparent that a timing arrangement is
necessary in the controller to identif~v the par~
ticular duration of the signal being returned over
sense conductor 41, and this will be explained in
connection with FIG. 13. For the present it is
sufficient to note that t~e timing is measured in
the controller, and thus neit~er the transponder nor
its associated transducer can initiate an alarm.
1~ In this em~odiment the controller determines and indicates
when an alarm or trou~le condition is present at a
specific transponder.
FIG. 6A indicates the response when a single
transponder is closing its switch S2, but in FIG. 6B
the response shown occurs when another transponder
(that is, a transponder which has not been addressed)
has its switch S2 failed in a shorted position. That
is, S2 of the other transponder remains closed through-
out the time period in which information is returned by
the addre~sed transponder. The ability to "read through"
this short is an important advantage of the present
invention. In FIG. 6A the negative-going excursions of
the first two pulses were between the lines 430 and 431.
These lines are similarly referenced in FIG. 6B. Line
430 represents a voltage level intermediate the V/2 and
V/3 levels, and reference line 431 represents a voltage
level intermediate the V/3 and V/4 levels. Line 432
denotes a voltage level between the V/4 and V/5
amplitudes. With ~2 of one tran~ponder closed, the
resistor R3 of that transponder is in parallel with
R2 of the controller, providing a voltage level of
Y/3 on sense conductor 41 as has already ~een
'
.
'
6~
8109~-BKR
-22-
explained. This is evident from the negative-going
excursions of the firstr second and fourth pulses
shown in FIG. 6A. However, with an additional
transponder having its swntch S failed în the
shorted position, an addit;onal R3 is paralleled
with the other resistors, and this produces a negative-
going excursion of the first, second and ~ourth
pulses to the V/4 level as shown in FIG. 6B. It
is apparent from inspection of the signal pattern in
FIG. 6B that the information can still be received
from the transponder and utilized, notwithstanding
the shorted output condition of the additional
transponder. Examination of the signal being returned
is readily effected by measuring khe time duration
during which the pulse amplitude remains at V~4,
from ~he beginning of interval 145 to the transition
150. The method of measuring this time duration
will be explained in connection with FIG. ll. By
measuring this time interval the controller is able
to read "through" the short and still determine the
information being provided by the responding trans-
ducer. This ability to read through (and also write
through) a transponder's shorted output is not
present in the prior systems and is an important
advantage of the present invention. Sequential systems
are usually dependent upon proper operation of previously
addressed transponders for a subsequently addxessed
transponder to return accurate information. In some
systems such improper operation prevents the return of
any information from suhsequently addressed transpondersO
Digital systems are usuall~ dependent upon proper
operation of all transponders. If any one transponder
~s its output element shorted, no useful information
can be received. If two or more transponders are sending
information simultaneously, again no discernible in-
formation can be received.
, :
,
;78
81099-~KR
-23-
F~G. 6C illustrates a different type o~ response,
where an additional transponder is not shorted ~ut
is nevertheless returning information concomitantly
with the addressed transponder. Again the first two
pulses reach the V/4 level, in that S2 of both
transponders are closed at the same time. However,
neither S2 is closed during the third pulse i~terval,
and hence the controller is a~le to determine there
is not a short at the second transponder, but
1~ instead both are providing information simultaneously.
During the stretched pulse interval 145, the initial
portion 160 of the pulse is at the V/4 level.
However, there is a first transition 161, followed
by a portion 162 at the V/3 level, and a second
transition 153 before the pulse returns to the Vj2
level in the final portion 164 of this pulse. If
both transitions 161, 163 are within normal window
147, as shown, the controller "knows" there is no
alarm condition. Should one response fall in the
2Q alar~ region, the controller "knows'l that one
detector is at the ala~m level, but at this time
cannot identify the precise detector returning the
alarm-level signal. Time interval 165 represents
the lower analog voltage value of the two being
~5 returned, and time period 166 represents the
higher of the two values. Had period 166 extended
into alarm window 148, the controller would have
determined that one of the t~o answering trans
ponders was returning an alarm-level signal.
3a FIG. 7 depicts the functional arrangemen~ by
which received signals issued by t~ controller are
processed with any transponder. As there shown
signals received over the line conductors 27, 28
:
:, .
~7~6~
81099-BKR
-24-
enter the signal~power separator 60, which ef-
fectively passes a d-c energizing potential difference
for the transponder components over line 61 to t~e
individual ones of those component~, and over line
62 to associated components (such as a detector~
~hen required. Those skilled in the art will
appreciate that the line 61 may represent several
conductors, such as a ground conductor, a conductor
with 5 volts with respect to ground, another with
12 volts with respect to ground, and so forth.
Signals received from the line conductors are
passed from the separator 60 to common bus 63,
which in turn passes the signals to an address
detection circuit 64 and an output command controller
65~ A plurality of address select switches represented
~y block 66 are individually coupled to address
detection circuit 64. The switches are simple on-
off switches, each of which can be set in the open
or closed position to collectively determine the
address of the specific txansponder in which the
circuit is located. With five switches in the illustrated
embodiment, up to 32 addresses can be individually
assigned by opening and closing dif~erent ones of
the switches. Thus these switches represent circuit
means for determining the unique address of the
transponder in which the switches are located. A
comparator or other arrangement within detection
circuit 64 recognizes coincidence of the address
received o~er bus 63 from the line conductoxs with
the un;que address set ~ ~witches 66 and, upon
recognizing this coincidence, provides an enable
signal over line 67 to both the analog conditioning
circuit 68 and the output command controller 65.
The analog conditioning circuit 68 includes
. . ~:
7~367~3
81099-BKR
-25-
means for recogni.zing when command information has
been received from the controller, and makes th.e ap-
propriate circuit connections required by such command
information. Analog conditioniny ci.rcuit 68 also
receives a first analog slgnal over conductor 70,
which ~n t~i.s em~odiment is zero volts, and a second
analog signal over conductor 71. The received analog
signal can ~e any type of information-connoting signal.
By way of example, a detector 72 is shown coupled over
conductor 71 to analog conditioning circuit 68. When
the circuit is directed to return information to the
controller concerning the analog signal r~ceived over
line 71, the analog conditioning circuit transmits the
response information signal, generated as a fu~ction
of the analog signal received over conductor 71, over
~us 63 and the signal/power separator 60 to the line
conductors, and thence to the controller. In this way
the sensitivity level of the particular detector can
be monitored in every cycle of operation if that is
desira~le or necessary under given conditions. A
reference or calibration voltage is provided over
line 73 to the analog conditioning circuit 68~
This reference voltage can be derived from a Zener
diode (not shownl or other suitable unit. The
reference or calibration voltage is returned to the
controller when requested, so ~hat the controller
circuitry can evaluate the operating condition of
the transponder. For purposes of this ~xplanation,
and the appended claims, line 73 represents means
for providing a reference voltage.
A plurality of de~ice i.dentity switches 74 are
also shown coupled to analog conditioning circuit
68. Like the other switc~es 66, identity switc~es
74 are simple open-closed or on-off switcAes, ~ut can
~e any suita~le means for completing a circuit to the
most negative or most positive power rails. Such switches
: ~ .
:.
~7~
81099-BKR
-26-
can be set to provide a numeri.cal combination ~from
1 through 8, in this embodiment~ to identify the
transducex type (such as detector 721 responding
oYer the line conductors. By way of example, the
setting of these switches can identîfy the type of
connected transducer as an ionizati.on-type smoke
detectox, a photoelectric-type ~moke detector, an
instrument signifyi~g air velocity, a temperature-
indicating unit, a mechanical s~îtch such as those
used with manual pull stations t.toggle type), a momentary
.switch of the type used to dump Halon, or some
other device. The analog conditioning circuit also
passes the signal indicating a particular command
has been recognized over ~us 63 to output command
controller 65, which is also enabled at this time
over line 67. T~is controller can accomplish
various functions. For example, one signal can
regulate an electromechanical actuator 75, shown as
a set-reset or on-off latching relay, to reset~ A
signal over line 76 can order this operation and
the illustrated contacts 77 will be displaced rom
the position shown to the alternate position (reset).
A signal from output command controller 65 passed
over conductor 78 can displace the contact set to
the illustrated (set) condition. Another possibility
is to pass an output command signal over line 80 to
illuminate a signal lamp 81, such as a light-
emitting diode ~LEDI.
A basic schematic of a transponder suitable
for operati.on with the present inv~ntion is shown
in FI~.. 8. A pair of screw-type terminals 83, 84
connect the line conductors 27, 28 to conductors
85, 86 of ~he transponder. A surge protector 87 is
coupled ~etween conductors 85, 86 to protect the
transponder components from transients on the line.
,
.
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~7~7~
81099-BKR
-27-
A diode 8B is coupled between signal line 85 and
power line 90 o~ ~he ~ransponder. A capacitor 91
has one side coupled to conductor 86 and its other
plate coupled to the common connection between
power condu~tor 90 and ~he cathode of diode 88.
When a long positive-going pulse is received at the
transponder, current flows through diode 88 to
charge capacitor 91. The charge on capacitor 91
maintains the voltage on power conductor 90 during
normal operation, when the lines are low, that is,
when the voltage across conductors 27, 28 is a~ V/2
or lower. This voltage on conductor 90 is applied
to the collector of an NPN type transistor 92,
which is connected as a series regulator to provide
a regulated output voltage on conductor 93. A
resistor 94 is connected between the collector and
the base of transistor 92, and the base is also
coupled through a Zener diode 95 to conductor 86.
A resistor 96 is coupled between conductor 90 and,
over line 99, to input connection 10 of integrated
circuit 1 (ICl).
When the voltage level on line conductors 27,
28 changes, there is a corresponding change in the
amplitude of the signals passed to pin 17 of ICl.
A low-pass filter, comprised of resistor ~7 and
capacitor 98, effectively blocks out high-fre~uency
noise pulses. In order for ICl to receive a low-
going pulse at pin 17, the signal level on conductor
27 must go low (to V/2) for at least one-half
millisecond before the low-going pulse is recognized
as a clock signal to IClo The voltage level on
conductor 110 is compared against the voltage level
on conduc~or 99, which is derived from the line vol~age
(across conductors 27, 28~ is used as a reference
. .
~L~.7~Çj7~
81099~BKR
-28-
signal to determine whether the clock signal is
high or low~ Utilization o~ this reference signal
compensates for large variations in th.e line voltage.
In the em~odiment disclosed, the system was found
to function accurately despite line voltage variations
from 15 to 30 volts~ a 2:1 voltage c~ange.
Other input signals are provided to ICl from
the arrays o~ on-off switches 66 and 74 shown to
the left of ICl. The first array includes switches
1-5 which~are the address select switches 66.
These are set ~y selective open;ng and closing
before the:equipment ls energized~ to determine the
unique addre~s of eac~ transponder. The second
array includes switches 6-8, which are the device
identity switches 74. These are set according to
the particular components (not shown) which are
coupled individually to the conductors 70 and 71
(FIG. 7). to provide the A and B analog input signals
to the integrated circuit.
Wh.en an output command is issued by the
transponder circui.try, the appropriate signal is
passed over one of the conductors 76, 78 or 80 in
FIG. 8. An output signal passed over line 80 energizes
led 81, coupled to conductor 86. An output signal
on line 78 is effective to energize the "set"
winding 101 of latching relay 75 and to close the
norm~lly-open contact set 102 of this relay. An
output signal over conductor 76 energizes the reset
winding 103 of the relay to close the normally-
closed contact set 104 of the relay. When thetransponder output circuitry pxovides a signal at
pin connection 8, over line 79 to gate on NPN type
transistor 10Q, resistor 89 wh.ich. in t~is em~odiment
.. . .
. , . , - ~
8~
81099-BKR
;2~-
is a 4.7K resistor, is effectively connec~ed between
conductors 85, 86, to pull do~n the amplitude of
the voltage then being presented to the controller.
Thus the operation of transistor lOQ in response to
the transistor control signals on line 79 is analogous
to the opening and closing of switc~ S2 as shown in
FIG. 3 and explained earlier in connection with the
transponder operation. It is apparent that resistor
89 ~FIG. 82 thus corresponds to the resis~or designated
R3 in the earlier discussions of the general system
operation.
It is important to emphasize that an output
command signal on line 79 to gate on transistor 100 is
only provided during a low portion of any signal
pulse. However the other a~tuating signals, to set
or reset relay 75 or illuminate LED 81, are provided
only during the high portion of a pulse; this is
important because the transponder utilizes energy
provided from the controller on lines 27, 28 to
actuate these components, without imposing any
drain on the energy stored in capacitor 91 which
energizes the components illustrated in FIG. 8.
Other components such as variable resistor 105,
fixed resistor 106, and the capacitors 107, 108 are
useful in connection with the circuitry of ICl.
A general block layout of the integrated
circuit is shown in FIG. 9, and a functional description
of the circuitry follows. The signal pulses in
each group received at the transponder are passed
over line 110 to input pin 17 of ICl, and thence to
clock pulse gener~tor stage 111~ This stage includes
conventional pulse shaping circuitry, such as a
comparator which compares the signal voltage lPvel
~L~7~i~
81099-BKR
-3Q-
on line 110 against the reference voltage level on
line 99. The clock pulse generator provides its
output to a 2-bit counter 112 and a clock identification
circuit 113. The clock identification circuit also
receives a reference oscillator ~ignal from resistor
106, capacitor 108, and conductor 93, also shown
in FIG. 8. A 5-~it counter 114 (,FIG. ~ is connected
to receive overflow pulses over line 115 from the
2-bit counter 112. ~hen the incoming pulse remains
high beyond a preset time (20 ms in t~e described
embodiment~, a "stretched clock" identification
pulse is passed over line 117 to a 2-to-4 line
decoder circuit 118. When the incoming pulse
remains high for a duration of 80 ms (in this
embodiment), stage 113 provides a reset pulse over
line 116 to both counters 112 and 114.
The 2-~it counter 112 provides a "clock decode"
output signal on its output conductors 120, 121.
Basically this signal idéntifies which o the
several possi~le commands is to be executed by the
transponder. This signal on lines 120, 121 is
passed to 2-to-4 line decoder 118, the 4-channel
analog multiplexer 122, and a switch logic circuit
123. The switch logic circuit is operative to
provide external switch operation "memory" for two
polling cycles of this transponder, should the
external switch be operated for a duration less
than two polling cycles. In this embodiment a
polling cycle ---the time interval between two
successive enable pulses being provided at the
output of stage 131 --- is three seconds. Thus the
memor~ duration for s~itch logic cïrcuit 123 is
from 3 to 6 seconds, d~pending on the exac~ time
in the polling cycle ~he'external switch is operated.
, - :
367~
81099~BXR
-31-
Such. an external switch.can be a momentary, mechanical
switch providing a signal over line 7Q and pin
connection 6 to the switch logic circui.t. It is
emphasized that notwithstanding the presence o~
this s~itch. and its actuation, the switch logic
circuit does not store the actuation indication for
subsequent transmission to the 4-channel analog
multiplexer 122, unless the appropriate switch.
identification information is received over t~e
three lines connected to pin connections 18, 19 and
20. These pin connections are connected to the
device identity (ID~ switches 74, as already explained.
If the device ID switches 74 are in the appropriate
combination to enable switch logic circuit 123,
then this stage 123 is conditioned to pass the
information regarding the switch actuation (at line
70) to the 4-channel analog multiplexer 122.
In the system of this invention r certain
combinations of the device ID switches coupled to
pin connections 18, 19 and 20 are effective to turn
the switch logic stage 123 on, that is, to open the
circuit between conductors 119 and 129 to the 4
channel analog multiplexer 122. In the preferred
embodiment 2 of the 8 possible switch combinations
were used to provide this operation. Under this
condition, the switch logic circuit 123 receives
the signal over line 70, pin 6, and line 119, and
operates upon this signal to provide a specific
state voltage ~hich is passed over line 12~ to
multiplexer 122. In the other 6 combinations of
the switches coupled to pins 18, 19 and 20, switch
logic stage 123 effects a straight-throug~ coupling
between lines 119 and 129.
1~78671~
81099-BKR
-32-
Opexati,on of the switch logic circuit will be
better understood wi.th.re~erence to FIG. 6A. W~en
the device ID si.gnal denotes a two-positi.on switch.
coupled to line 70, the information received ovex
line 119 from th,~ switch must be "translated" or
converted to identi.fy one of the 3 possi~le states,
either not connected, open or closed. Alternatively,
a temperature sensor device coupled to line 70
would produce an analog output signal, and the
device ID signal would dictate a straight pass-
through of this information, without conversion in
switch log;c stage 123.
A generator circu;t 124 is provided to develop
the device identification (ID) signal and calibration
(reference), signal. The ID signals are applied
over a plurality of conductors represented by bus
125 to an 8-channel analog multiplexer 126. The
switch ID output signal from multiplexer 126 i5
passed over line 127 to the 4-channel analog
~ultiplexer 122, which also receives the calibration
voltage signal over line 73 from generator 124.
Multiplexer 122 also receives the analog A signal
over conductor 71, and the analog B signal received
over line 70, via lines 119 and 129, when the
circuit is completed by switch logic stage 123.
The output of multiplexer 122 is passed over line
128 to a voltage-controlled one-shot stage 130,
which has connections as shown to the variable
resistor 105 and capacitor 107 in ~he lower right
portion of FIG. 8.
A digital comparator circuit 131 (FIG. ~), is
connected to receive the outputs from 5-~it counter
114, and ~he inputs from the address seIect switches
66. Upon recogn;tion of coincidence ~etween the
. .
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6'~
81Q99-BKR
unique transponder address determined by ~hese
switches and the address represented by the pulses
transferred from counter 114, digital comparator
131 passes an enable signal o~er line 132 to the
voltage-controlled one-shot 130, and t~e enable
signal is also passed over line 133 to the 2-to-4
line decoder 118. The output of the clock pulse
generator on line 139, when high, resets voltage-
controlled one-shot 130. When this clock output signal
is low, this provides a second e.nable signal to stage
130. The voltage-controlled one-shot stage 130, upon
receipt of both enable signals, functions to provide
an "energize" output signal on line 134 which is
amplified in the appropriate one of the output drivers
135~ a.nd passed over the output pin connection 8 of
ICl. Pin 8 is selected whenever the transponder is
sending information back to the controller. This is
analogous to gating of transistor 100 in FIG. 8, or
closure of switch S2 as explained above in connection
with FIG. 3.
To select any of the other output pin connections
136 (1, 2, 3 or 4), the 2/4 line decoder 118 must
provide an appropriate output signal on one of its
four output lines 137. This requires three signals to
decoder 118: (11 clock decode output on lines 120, lZl
which selects the output driver to be energized; (2
enable signal on lin. 133, corresponding to a "trans-
ponder select" signal; and (3) another enable signal
(:"stretched clock."~ on line 117, which signifies the
command hac indeed been i.ssued. Selection of pin 1
ma~ be used to energize an associated alarm apparatus,
~ut pin 1 is not used at this time. Selection of pin 2
indicates t~a~ LED 81 is to ~e energixed. Selection
of pin 3 is equivalent to providing a signal on
conductor 78 (FIG~ 7) to set the latching relay, and
.
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1~L7~6~
8109g-BKR
-34-
selection of pin 4 i.s equi~alent to providin~ a signal
on conductor 76 to reset th.e latching relay~
The foregoing functional descripti.on is sufficient
not only to ena~le one skilled in the art to provide
an appropriate specific circuit design for IC1 in FIG.
8, but by explaining the entire functional sequence,
it further enable~ one skilled in the art to implement
the circuit operations with various circuits, or to
regulate differ~nt ou~put functions as may be desired.
Now that the operation and circuit arrangement of the
transponder has been set forth, it will be heLpful to
consider the manner in which controller 26 operates
upon the information returned from the transponder to
derive and utilize useful signals and provide ap-
propriate indications.
FIG. 10 shows in idealized form a return pulse,that is, a "stretched" pulse low similar to that
designated i44 in FIG. 6A. The pulse low in FIG. 10
is designated 180, and like the other pulses occurs
during a time interval of 32 milliseconds (in this
embodiment) from the leading edge 181 of the pulse to
the trailing edge 182 of the pulse low. The stretched
low 180 includes an initial low portion 183, a positive-
going portion 184, where the signal goes from the V/3
to the V/2 level, and a final portion 185. Ref~rence
line 186 indicates the alarm threshold, and the lines
187, 188 depict the range of adjustable sensitivity.
As a practical matter, the actual sensitivity is
represented by the diference between line 184 of the
pulse signal and the alarm threshold line 186. In a
preferred embodiment an 8 ~olt measurement ra~ge was
depicted over 32 milliseconds, with the initial portion
183 of the pulse low representing the analog input
:, .
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7~36~8
81099-BKR
value from the transponder to the controller. How-
ever, as a practical matter the returned information
is not represented with an ideal waveform of the type
depicted in FIG. 10. Rather the YariOuS transitions
are distorted by the components in th~ system, to
produce transitions of the type generally represented
in FIG. 11.
FIG. 11 s~ows a "real-life" pulse, produced with
some line capacity effects. As there shown t~e
initial edge 192 of the actual response does not
descend vertically ~ut follo~s a generally logarithmic
curve. In this returned signal, the end or the
analog or information period is represented at the
positive-going portion 193, w~ich likewise is curved
rather than a sharp, vertical displacement. Because
these are critical portions affecting the measurement
of the V/3 level portion, it would be desirable to
have some vernier or more precise measurement during
these two transition periods. On the "coarse range"
time scale 194 the units are sepa~ated by one milli-
second (ms) intervals. It would be helpful to have
another time scale, delineated as "vernier range" 195,
where the units are separated in smaller intervals,
such as one-half or one-quarter ms, to provide a more
precise recognition of the pulse ~ransitions and thus
a more accurate derivation of the exact analog value
represented by the low or zero level of the returned
signal. Such a measurement, for this enhanced accuracy,
is made on different time scales during different time
periods as represented in FIG. 12.
As there shown, ~e~ore any measurement starts the
apparatus is at the 1 level or in the non-measuring
mode. At time 0 ~zero millisecondsl an appropriate
r~
81099~BKR
-3~-
measuring apparatus is switched in, operating on the
vernier scale for the first 2 milliseconds of the
return pulse, represented as the 3 leveI in FIG. 12.
After the time of the initial transition, t~e measuring
apparatus can operate at a more coarse level identified
as level 2, until half the period or 16 milliseconds
has expired. In t~is example the alarm thres~old is
"po~itioned" during the following 4 milliseconds, and
hence the measuring apparatus is returned to the
vernier or fine measurement mode for this time interval,
from 16 to 20 milliseconds. For the remainder of the
pulse return period, from 20 to 32 milliseconds, the
apparatus can ~e returned to, and left in, the coarse
measurement mode, and switched off at the expiration
sf the period. For other voltage ranges to be transmitted
and different degrees of precision desired with the
vernier measuring system, those skilled in the art
will appreciate that changes in the voltage ranges
and/or measurement intervals can readily be implemented.
FIG. 13 depicts in simplified form the arrangement
in controller 26 for operating upo~ the signal returned
from the transponder and passed through comparators
51, 52 to provide useful information such as "alarm",
"trouble", and so forth. Basically, the system
receives the signal on line 54 when one transponder
is responding with a V/3 level signal, and this
signal is passed over switch 200 and line 201 to two
AND circuits 202, 203~ Command circuit 42 is ~onnected
to regulate operation of switch 2Q0, as well as two
additional three-position switches 204, 205. These
latter switches are "ganged" or mechanically intercoupled
., . :
7~
81099~BKR
-37-
for simultan~ous actuation between the three positions
illustrated. The circuit effects of the switching
functions represented by switches 200, 2Q4 and 205 are
actually accomplished, in a preferred embodiment,
under the control of an algorithm stored in the
memory portion of the CPU used with t~e system.
However, the mechanical switch illustration serves to
depict the manner in which the signal~ and pulse
trains are routed, ta~uiated and utilized to provide
an appropriate "ans~er" signal from which significant,
useful data are received from the appropriate trans-
ponders and/or intercoupled transducers.
Switches 204 and 205 have their switch contacts
designated 1, 2 and 3 to indicate mechanical positions
corresponding to the showings in FIG. 12 of the off
(or non-measuring mode) 1, coarse measuring mode 2,
and vernier or fine measuring mode 3. Basically the
system provides a pulse train from an oscillator 206
(FIG. 131 over the switches 204, 205, for passage
through the ~ND circuits so long as the signal on line
201 indicates the analog information is being returned
from the transponder. The low level signal 183 shown
in FIG. 10 is applied over line 54 to line 201 to gate
the pulse train through one of the AND circuits to the
then-ef~ective counting system to provide an "answer"
signal on line 2Q7.
In more detail, oscillator 206 can be a conven-
tional pulse genera~ing unit operable~ in the illustrated
embodiment, to provide a pulse train at a frequency
of 4,000 cycles per second. This frequency is chosen
in relation to th~ duration of the returned analog
signal and other considerations, including the degree
of precision desired for operation in the vernier
~7~1~7~
81099-BKR
-38-
measuring mode. The oscillator signal is provided on
line 208 directly to a divide-by-4 circuit 21Q and
over line 211 to position 3 (for fine counting of
switch 205. The output of divide-by-4 circuit 210 is
coupled over line 212 to position 2 of switch 204, the
contact engaged during coarse counting. The movable
contact of switch 204 is coupled over line 213 to one
input of AND circuit 203, and the mo~able contact of
switch 205 is coupled over line 214 to one connection
of AND circuit 202. The output of AND circuit 202 is
coupled over line 215 to a fine counter 216, which ac-
cumulates the total number of pulses received on line
215 and provides a signal on line 217 repxesenting that
total. Likewise the output of AND circuit 203 is
coupled over line 218 to a coarse counter circuit 220,
which accumulates the total number of received pulses
and provides on its output line 221 a signal repxesenting
that total. This signal is passed to a multiply-by-4
sta~e 222, which multiples this resultant signal on line
221 by 4 and provides the net result on line 223. The
signals on lines 217 and 223 are then combined in adder
stage 224, providing a resultant signal on line 225.
Those skilled in the art will appreciate that the counting,
multiplication, division, and addition (or algebraic
summation) of the various signals can be implemented with
analog or digital techniques, but in this embodiment the
arrangement has been implemented wi~h a digital system.
The output signal on line 225 is coupled to another adder
stage 226, which also receives a compensation signal
over line 227 from compensation stage 228. The precise
compensation provided by stage 228 may vary as will be -
explained later. The output signal from stage 226, on
l~ne 207, is thus an answer signal representing the time
duration during whic~ t~e s-tretched low pulse 180
.~
: :: ~
81099-BKR
39-
(FIG. 10) of the transponder respons~e remained low, at
the V~3 level~
Common line 207 (FIG. 13~ provides ~he answer
signal over line 230 to a first comparator 231, which
includes an output l;ne 232 for providing an alarm-
indicating signal when warranted by th~ value of the
answer signal and the setting of multiple position
switch 233. As shown, this switch is displaceable to
one of three ~in this em~odiment~ settings ~y adjustable
sensitivity stage 2~4, whic~ can be controlled over
line 235 from a program stored in the memory (not
shown) of ~he digitaI s~stem controlling the~operations,
or over line 236 from a keyboard or other terminal
(not shown) interfacing with the system~ The stored
program can modify the position of switch 233, prior to
comparing the answer signal, for each transponder
connected in the system. This makes possible the assign-
ment of any sensitivity setting to any detector on
the system. Such control of switch 233 represents the
function of adjustable sensitivity, as each detector
can have its sensitivity adjusted from the control
panel without taking the system out of operation. By
chan~in~ the position of switch 233 to engage different
contacts, where the number adjacent the contact denotes
the value o~ ~he alarm threshold value, the answer signal
on line 230 must equal or exceed this number represented
by the setting to provide an alarm-indicating signal
on output line 232. The numbers 65, 75 and 85 represent
sensitivity thresholds on a scale of 0 to 128, a scale
achieved by multiplying the 32 millisecond response
interval b~ four~ The reason for t~is will become
apparent in the su~sequent operational description.
The answer signal on line 207 is also applied
over line 240 to another comparator stage 241, which
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78
81099-BKR
-40-
receives another reference input signal over line 242.
This comparator is connected so ~h.at wh.en the answer
signal on line 207 is less than or equal to t~.e reference
signal on line 242, a trouble-indicating signal is
provided on output line 243.
In operation r it is initially understood that
controller 26 has "told" an addressed transponder to
return information, and ~hus command circuit 42 in
FIG. 13, at the beginnin~ of the response period,
place.s switch 200 in the illustrated position.
Switches 204, 205 are displaced to position 3, for fine
counting. Thus, at this time oscillator 206 is passing
signals over line 211, switch. 205, and line 214 to one
input of AND circuit 202. As soon as the fourth or
stretched lo~ commences t the other input to this AND
is provided over line 201 from comparator 51, so that
the pulse train is passed over line 215 and registered
in counter 216. Suppose the leading edge 192 (FIG.
11~ of the responding pulse reaches the V/3 level
after 1.5 milliseconds, or 6 counts on time scale 195,
then the remaining 2 pulses or counts are passed
through AND circuit 202 (FIG. 13) to counter 216.
This occurs because command circuit 42 maintains
switches 204, 205 in position 3 for the first 2
milliseconds of the response period, after which the
switch contacts are displaced to position 2 fox coarse
counting. Accordingly, the AND cixcuit 202 is effectively
removed from the circuit, and AND circuit 203 i5
coupled over switch 204 to stage 210. Thus the train
of pulses from oscillator 206 is divided down in stage
210, and applied over line 212, switch 204 and line
213 to AND circuit 2Q3. The pulses are now effectively
at 1,000 cycles, or one every millisecond, as represented
on time scale 194 in FIG. 11. In that switches 204,
~L71~6~3
81099-BKR
-41-
205 remain in position 2 during the interval from 2
milliseconds to 16 milliseconds, 14 pulses are passed
over line 218 and accumulated in counter 220. This
number is effectively multiplied in stage 222 to
provide a value of 56 on line 223, whic~ is added in
stage 224 to the value (two) previously received over
line 217. At this time (16 miIliseconds~ adder staye 224
registers a count of 58, and switches 204, 205 are
returned to pos;tion 3 for fine counting.
Assuming that transition 193 (FI~ occurs at
18 milliseconds, then 8 pulses are passed from the
oscillator over switch 205 and AND stage 202 to register
in fine counter 216, in the time interval ~etween 16
and 18 ms, and this count is passed over line 217 for
addition in stage 224. These 8 pulses are added to
the previous total of 58, and thus the total in addex
stage 224 is now 66. At time equal to 18 ms, the gating
signal is no longer provided from line 54 to line 201.
After 20 milliseconds (from time 0~ the switches 204,
205 are restored to position 2 for coarse counting,
but as noted there is no longer any gating signal present
to gate the pulses through AND stage 203 to the coarse
counter. At this time the signal on line 225 is
passed to adder stage 226.
Cornpensation stage 228 can be used to modify the
preliminary result at this time. For example, if the
last interrogation of the particular transponder
indicated a "reference" signal voltage had risen from
4.0 volts to 4.06 volts, due to aging of the system
components or other long term system change, the
result on line 225 could be modified by substracting 1
from the count of 66 to provide a new count, 65, for
comparison to the alarm thres`hold level and similar
7~6t78
81099-BKR
-42--
use in the other processing stages. Accordingly, it
is assumed that a count of 65 i~ the answer signal on
line 207 which is passed to the comparators 231, 241.
Comparator stage 231 is connected over switch 233
to a relatively lo~ sensitivity level of 65, representing
~5/128 of R volts, or a~out 4.06 volts. Because the
signal on line 230 ~a total of 65~ is equal to the 65
reference signal on the other input of comparator 231,
an alarm output signal is provided at this time.
1~ operation of comparator 241 determines t~at 65 is
greater than its reference ~nput 35 ~representing 2.19
volts~, and thus no trou~le signal is provided on line
243. Other processing stages will be described below
in connection with FIGo 15. However, it is important
to emphasize that the system illustrated in FIG. 13
provides a very high degree of precision in converting
the analog signal on line 201 into the digital answer
signal on line 207, even though the ine mode of
counting is only employed for 2 milliseconds at the
initiation of the response signal and 4 milliseconds
near the middle of the response time. In a broader
sense a vernier operation at a frequency higher than a
reference frequency is utilized in a limited time span
to provide accurate and effective measurement over a
much longer time span.
FIG. 14 shows a system for obtaining an "answer"
signal on line ~07, from one of a plurality o~ zones
in which different transponders and transducers are
located. Each zone provides an information-denoting
signal over its respective conductor 41A, 41, 41B, or
41N. This is analogous to the showing of different
conductor pairs in FIG. 17 under the regulation of a
plural~ty of controllers 26. Thus the various swi~ching
functions shown in FIGURES 13, 14 and 15 are represented
: ; , : ' ;
:
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.
7~
81099~BKR
-43-
as regulated by a command circuit, that i5, regulated
by a CPU and associated program, and a plurality of
controllers 26. The multipIe zones dep;cted in FIG.
14 have their respective information signals analyzed
and evaluated ill the mul*~ple channels shown ~n FIG.
14, and provide on their respec~ive output conductors
251, 252~ 253 and 254 different "answer" signals
representing the respective zone conditions. Command
circuit 250 then activates switch 255 for sequentiaI
connection to the various output conductors 251, 254,
and provides only one "answer" signal on conductor 207
at any given time.
Those skilled in the art will appreciate that the
routiny of individual zone signals can be accomplished
under the direction of the program stored in the
controller or associated with the CPU ~not shown), to
provide an operation which is the functional equivalent
of the switch arrangement shown in FIG. 14.
FIG. 15 illustrates an arrangement ~or operating
upon the "answer" signal developed as explained in
connection ~ith FIGS. 13 and 14. Again the circuit
illustration depicts the translation and/or manipulation
of data to provide the desired functional output.
Such manipulation can be under the control of the
stored program, but the hardware illustration is
useful to explain the underlying system arrangement
and operation.
FIG. 15 sho~s the "answer" signal is distributed
over bus 207 for presenting "answer" data to various
operational stages. The processing of this data to
obtain the "alarm" and "trou~Ie" signals has already
~een descri~ed. As shown in FIG. 15, a divide-~y-16
stage 260 is coupled to line 207~ Since 128 counts
represent a voltage amplitude of eight volts in this
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1~.7~
81099-BKR
-44-
embodiment, then dividing 8 by 128 (as in dïvide-by-
16 stage 260~ establishes a ratio for converting the
answer signal on line 207 into a signal (on line 261)
representing the actual transponder voltage. Thus
an answer signal value of 67 (for example) would be
divided in stage 260 and produce an output value of
4.2, signifyîng 4.2 volts r on line 261. When a Zener
diode or other device is used to produce a calibration
voltage of 4.0 volts at a transducer, this results in
an answer signal of 64 on line 207, which is divided
by stage 260 to prsduce a calibration voltage value of
4 . O volts on line 261.
~ nother divide-by-16 stage 262 is coupled over
line 263 to the movable contact of switch 233, which
receives the selected aIarm threshold voltage. Suppose
switch 233 is positioned to the center or medium
threshold setting, identified with a count of 75 in
the drawing. This value is passed over line 263 and
divided down in stage 262 to produce a value of approximakely
4.7 volts on line 264, the input connection to summation
stage 265. With a voltage of 4.2 volts passed over
lines 261, 266 to the negative input of stage 265,
this stage provides an algebraic summation of these
values, subtracting 4.2 volts from 4.7 volts to provide
a resultant value of 0.5 volt on output line 267.
This resultant value is thus a measure of the trans-
ducer sensitivity, as it indicates how "~ar" the
transducer is from the alarm threshold. If the voltage
increases another 0.5 voltr the actual voltage will
reach ~he alarm threshold and provide an alarm signal
on line 232. By monitoring the long-term change of
sensitivity value on line 267, the controller record
ran sho~ changes due to component aging, dust accumulation,
and similar effects. This sensitivi~y value on line
:~ ~
. ., :
~ ~ ~7~
81099-BKR
-45-
267 is a significant measurement and provides in-
for~ation at the controller which has not previously
been o~taina~le.
Coupled to line 207 is another albegraic summation
sta~e 27Q, whIch also receives the "answer" signal
oyex Its 1nput l~ne~ 271. A storage stage 272 i5 also
coupled, over l~ne 273, to ~us 2Q7. ~en the equipment
is originally installed, the desired cali~xation
signal is returned from each transducer, t~rough its
transponder. This ini~ial calibration signal is
stored ;n stage 272, provid;ng a benc~mark for sub-
sequent reference. Thereafter in the "Sunday morning"
poll, a measurement taken at a low-occupancy, quiescent
time such as 2:00 a.m. Sunday morning, a calibration
signal is returned over lines 207, 271 to stage 270.
The original stored calibration signal is passed over
line 274, and suhtracted fxom the "Sunday morning"
signal in stage 270. T~e resultant compensation
signal on line 275 is a measure of the long~term
changes in the circuitry, the electric conductors, and
the other varia~les which affect the generation and
transmission of the c~libration voltage. Thus the
signals on lines 275 and 308 or a portion thereo~ can
be used to modi~y the data, for example, to raise/lower
the answer signal as the compensation signals change,
to help mai`ntain the normal operating sensitivity of
the system.
Stage 400 is coupled over line 4Ql to stage 270,
to receive a si~nal denotin~ the extent of the change
in the original calibration signal. A reference level
~ignal i5 applied over line 4Q2 to stage 400, and when
the cali~rati`on variation signal exceeds the reference
level, a "maintenance required" signal is provided on
line 4Q3.
The device ID signal is derived by passing the
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81099-~KR
-46-
"ans.wer" signal on line 207 over line 28Q for examination
by a series of com~arators 281-288, only the first and
last of which are depicted. The devi.ce identi.ty
switches 74 are represented generally in FIG. 7 and in
more deta~.l in FIG. 8. Th.e switch ~ettings are translated
in multipiexer 126 CFIG. ~ ~.nto a s~i.tch ID signal on
line 127, and then passed to the controller as ~as
already been explained. Thus, the ~ignal on line 280
~.FIG. 15) is one of elg~* different values, ~ith the
precise value to ~e determined by the serie~ of comparators
281-288. For example, a "type 1" si~nal may identify
a smoke detector of the ionization type, and if the
signal on line 28Q îs within the range predetermined
by the input signals supplied over conductors 290, 291
to comparator 281, then an output signal is provided
on conductor 292 to indicate the connected device is
indeed a "type 1" unit. In this way the voltages
establ~.shed ~y the different comhinations o~ the ID
switch settings are e~fectively decoded and used at
the controller to identify the particular device then
returning information through its associated transponder.
Reference has been made to the "Sunday morning"
service, a term u~ed to indicate a sequential poll of
the transponders and storage of the data returned,
which. poll is at a ~requency substantially lower than
the normal pollîng frequency, and is preferably taken
at a time when the premises are v-.rtually unoccupied
and thus guiescent. At such a time the conditions in
the controlled areas will have stahilized 9 and a
sample poll taken at thi:s time is useful to obtain
reference information. For example, th.e respon~e
volta~e of a tran~ducer can be recelved, and then
comp~red to th.e initial transducer response to determine if
ther~ has been any c~ange in t~is re~ponse signal.
J
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~;7~
81099--BKR
-47
The three stages 300, 301 and 302 shown at the
bottom o FIG. 15 are utilized only in the less-
frequent poll, the "Sunday morning" po}1. The original
trans.ducer response received in the first Sunday morning
polI after system start-up is passed over line 303 and
stored in stage 30Q, and this value is not changed
thereafter. In each subsequent weekly poll, the
response on line 207 is passed over line 304 to the
alge~rai.c su~nation stage:301, in which the ariginal
transducer response (from stage 300~ is subtracted,
providi.ng a resultant output signal on line 305.
Stage 302 is a simple comparator to determine whether
the amplitude of the signal on line 305 -~- and thus
the extent of the transducer response change ---
falls within an acceptable range. In the event theextent of the signal variation is greater than that
denoting an acceptable range, a signal is provided on
line 307 to indi.cate maintenance is required. Such a
signal can ~e a visual signal, such as illuminating a
lamp in a panel~ or an audible signal varying in some
predetermined manner, or physical displacement of a
"flag" or indicator, or some other indication. The
precise device and manner of using the "maintenance
required" signal is not critical. It is important to
2S note this is an extxemely useful signal 9 as it alerts
the equipment user to the need for maintenance before
a malfunction or erroneous signal can occur.
' ''
.
.
81099-BKR
-47-A-
Another important feature of the invention is
that select;ve and remote~calibration of any trans-
ponder can be effected. This:can be accomplished
at any transponder, ~y changing the five address
select ~witches (21-25,.FI&S. 8 and 9~ to register
addxess 31. The controller is then operated to
examine the cali~rat;on voltage retuxned from this
transponder and, if the voltage falls within
acceptable limits, to indicate this by illuminating
the LED at the transponder. Other actions, such as
setting of the relay, can be used to indicate the
acceptable range of the calibration voltage. If
the calibration rPturn is not within the preset
limits, a variable resistor (105, FIGS. 8 and 9)
is adjus:ted until the callbration is correct as
signalled by the LED. After the correct cali-
bration is verified, the address select switches
are returned to their original settings.
FIG. 16 shows a general arrangement of a Class A
system with.a plurali.ty of transponders 25a and 25b
connected ~or energization over the loop. Controller
26 includes a pair of conductors 311, 312 over which
the voltage signals are sent and receivedO Conductor
311 is coupled to a scre~ terminal 313 and a conductor
segment 314. Conductor 311 is al50 coupled over a
normally-open contact set 315 to another screw terminal
316, which is connected to another conductor segment
81099 BKR ~7867B
-48-
317O Segments 314, 317 are connected h.y a short
conductor segment 318 to form a continuous electri.cal
circuit extendin~ from line 311, over.screw terminal
313, line se~ment~ 314, 318, 317, and scre~ terminal 316.
Line 312 is coupled over anoth.er screw terminal
320 to a line conductor segment 321. L~ne 312 is also
coupled over a normally-open contact set 322 and anoth.er
screw terminal 323 to a conductor segment 324.
A sh~rt segment 325 of a line conductor completes the
electr~cal path.~oetween segments 321 and 324. A
resistor 326 is coupled ~etween term;nals 316 and 323,
to provi.de the function of resistor R2 in FIG. 3.
In normal operation it is apparent that an
energizing potential d;fference and voltage signals
can be applied to all of the transponders over con-
ductors 311, 312. Fox example, when the potential on
l~ne 311 is positive with respect to that on line 312,
current flows from line 311 over terminal 313, line
segments 314, 318 and 317, transponders 25a and 25b,
line segments 324, 325 and 321, and ~crew terminal 320
to conductor 312. Suppos-e however that a break occurs
in line segment 317 at the location designated 327.
All transponders would no longer be in the loop over
the just-described circuit. Transponders 25b still
receive power, ~ut are not connected to resistor 326;
therefore data from transponders 25b cannot be received
at resistor 326. Transponders 25a are no longer powered
and therefore cannot function. In accordance with
normal Class A operation, ~h.en-this occurs contact
sets 315 and 322 would ~e closed (by means not illustrated
but ~ell-kno~n and understoodl. In spite of the
~reak, the three transponders 25b to ~he rig~t in FIG.
16 are now-again connected_to resis~or 326, and trans-
ponders 25a are now energized as current flows from
~7~,
81099--BKR
-49-
line 311 over contact ~et 315, screw terminal 316, and
line segment 317 to the transponders 25a. In earlier
arrangements the contact sets were closed and it was
assumed that the transpondexs were returned to service
by this operation. However, with the present invention
there are advantages not o~tainable with previous
Class A systems.
For Class A operation with the present invention,
contact sets 315, 322 are closed, the transponders are
again polled, and the addresses of the replying trans-
ponders are noted. If all transponders are now replying,
t~en the application of the Class A circuit restored
proper operation of the system. This demonstrates that
there was only one break on one or both sides of the loop.
This proof that the system is again fully operational
is not available from prior art systems. Hence, the
operation of the present invention with a Class A
system is a substantial advantage over prior arrange-
ments.
There may be two or more breaks in the conductor
loop including segments 314, 318 and 317, or in the
other loop. With prior art Class A systems, the normally-
open contact sets 315, 322 would be closed. However,
with those earlier arrangements, there i5 not positive
recognition that the contact closure, or other Class A
circuitry, has failed to restore the system, and that
the transponders are non-operative. With the present
invention, those transponders are polled and it is
determined, from the failure to respond, that the system
is inoperative by reason of a multiple break, and
those transponders still not replying are specifically
and individually identified.
To illustrate Class B wiring~ ~IG. 16 is modified
as follows. Line segments 314 and 318 are removed,
and replaced ~y a jumper 319 connec~ing screw terminals
313 and 316. ~ikewise on the other loop, line segments
.
:.
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~L~7~
81099-BKR
-50-
321 and 325 are removed, and replaced by a jumpex
320. With a single break as shown at 327, the location
of the break can be determined as ~eing between two
specific detectors. In the modified system of FIG. 16,
the controller polls the system and notes th~e addresses
of those transponders vhich do not respond. If all
transponders on the loop are sequentîally addressed,
then the ~reak is located between the last responding
transponder and the first transponder not responding.
With additional information it i5 also possible to locate
the break with non-sequentially addressed transponders.
The term "controller", as used herein and in the
appended claims, refers not only to the controller 26
shown in FIG. 3, but also to a central processing unit
(CPU) and its associated program. FIG. 17 illustrates
the association of a CPU 330, over a bus 331, with a
plurality o~ controllers designated 26, 26a, up to 26n.
A plurality of controllers ~6, 26a, . . . 26n, can share
the storage and processing capability of a single CPU.
In addition, input device(s) 332, such as a keyboard,
can be coupLed to the CPU to insert information such
as a request for a response from a particular trans-
ponder in a designated zone. Suitable output device(s)
333, such as a printer, loudspeaker, CRT display, or
other arrangement can be provided to indicate the status
of the data processed by the CPU. Accordingly, it is
again emphasized that the term "controller" includes
not only the actual control circuits but also a central
processing unit, at least on a shared basis. Those
skilled in the art will recognize that a CPU on a chip
(integrated cîrcuit chip) can be provided with the
controller circuitr~ in a compact arrangement.
:
~7~367~3
810~9-BKR
--51--
With this understanding of the controller, it is
appropriate to emphasize the subs:tantial flexibility
which such a controller imparts to th.e inventive
system, and the ~road extent of the information included
in the controller output si~nals. This will ~e set
out in connection ~ith FIGS~ 18 r l9A-19F, and 20A-20F.
While these waveforms are not precisely to scale, one
inch on the abcis~a of each waveform represents a time
duration At 32 ms.
Considering first the showing in FIGo 18 ~ the 5
pulses there shown include 4 pulses of one pulse group
representing both înformation and a particular trans-
ponder address, akin ~o the four-pulse groups shown in
FIGS. 6A-6C, and an elongated pulse such as the signal
shown at address 31 in P'IG. 4. In FIG. 18 the low
level of the pulses represents the condition with
controller switch Sl (FIG. 3) open, and the high
amplitude denotes the condition with Sl closed. The
rise and fall of each pulse indicates a closing or an
opening of switch Sl.
In FIG. 18, the rise of the first pulse at time
tO is provided as switch Sl closes, and this conveys
certain information. The switch closuxe and consequent
pulse rise commands the previously-replying transponder
to termina~e its transmission, and further "tells"
every transponder to increment its respective counter.
This is done in order that the individual pulses, and
thus the pulse groups, can be tallied so that the
successively addressed transponders recognize their
individual addresses. After Sl has been closed, if it
remaîns closed for a predetermined minimum time (repre~
sented as the duration ~etween tO and t2)l t~e command
is given to the transponder to turn on its output ~l.
In the described system, this is represented by a
signal at ou~put pin l of the output dxiver array 135
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7l3
81099-BKR
-52-
in FIG. 9. The other output pins 2-4 are also xelated
to the commands embodied in the second, third and
fourth pulses in FIG. 18. Because the pin 1 connection
of the output driver is not used at this~time, the
fact that the command issued by stretching the first
high pulse past t2 does not produce an output action.
At time t3 Sl is opened, t~e pulse goes low-, and this
aCtiQn tells the addressed transponder to terminate
its output ~ y removing the signal from pin 1 in
FIG. 9), and aIso for the transponder to begin trans-
mitting its calibratiQn data~ Note that if the pulse
had gone low at time tl, this indicates that the #l
output of the addressed transponder is not to be
turned on.
After time t3, if switch Sl is left open in the
controller, the duration of the low level signal
between t3 and t4 can be up to 32 ms, in that 32 ms
was the time duration chosen for the preferred embodiment.
Of course, the low level signal is continuously
sampled as has been explained to determine where the
transition occurs, and thus indicate the actual. value
of the calibration data returned to the aontroller.
If the controller does not desire the return of calibration
data from the addressed transponder, Sl is again
closed after only 1 or 2 ms so that the time between
t3 and t4 would thus ~e 1 or 2 ms. It is apparent
that each rise and fall of every pulse in the pulse
group provides information and/or commands to the
addressed tran~ponder, or to all the transponders.
~t time t4 Sl is closed and th.e pulse goes high,
either terminating the transmission of calibration
data or preventing it, and incrementing the counters
of all the txansponders. Switch.Sl is again opened at
time t5 and the pulse goes low, before the time ~t6)
; :
---~ 1.'17~67~3
81099-BKR
~53-
at which the high level pulse ~ould have commanded the
transponder to turn on its output #2. In this case
that would have meant driving pin 2 of driver array
135 high (FIG. 91, and illuminating LED 81 (F~GS. 7
and 8~. How~ver, t~e pulse did go lo~ at time t5,
which signifies that ~ere is no action to ~e taken at
the #2 LED outpùt. During the time between t5 and t8,
the transponder is allowed to return the I~ data. Had
the pulse gone high soon after t5, the transponder
would not have been allowed to return this data.
At time t8 Sl is again closed and the pulse goes
high, terminating the transmission of ID data and
incrementing all the counters. The third pulse remains
high, with switch Sl open, only to t9. At this instant
Sl is opened, prior to the time (tlO) to which the high
pulse level must be extended to command the transponder
to drive pin 3 high in the driver array 135, an a~tion
which commands the setting of relay 75 (FIG. 7). Thus
the opening of swit~h Sl at kime t~ is in effect a
command not to set the relay. The pulse remains low to
tl2, an extended time during which the transponder is
allowed to return information corresponding to the analog
1 input, on line 70 in FIGS. 7-9. The analog value of
this signal is derived in the transponder as explained
above in connection with FIGS. 11-15. At time tl2 switch
Sl is again closed, sending the pulse level high in
FIG. 18, terminating the response from the replying trans-
ponder and incrementing all the counters.
The fourth pulse must remain high for a predetermined
time interval, represented as the distance between tl2
and tl4, to order the transponder to turn on its ouput #4
and thus reset the relay. Had the pulse gone low at time
tl3, the practical ef~ect is to tell the transponder
not to reset the relay. However, the pulse remained
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high past tl4 to time tl5, and thus the command is
issued and the relay i5 reset. Between times tl5 and
tl6, the transponder attempts to return the information
from the second analog device, received over conductor
71 as shown in FIGS. 7-9. However, as shown in FIG. }8,
it is assumed that switch Sl is closed after only 1 or
2 ms, which in effect tells the transponder not to transmit
the data from the second analog de~ice. At time tl6
Sl is again closed and t~e pulse level goes high,
praventing transmission of the analog 2 information
and incrementing all the counters.
The four pulses just described constitute one
pulse group, addressing a single transponderO Thus
at time tl6 the address of the next transponder in the
address sequence (which is not necessarily the next in
physical locationl is commenced. The fifth pulse stays
low past time t22. Had the pulse gone low by opening Sl
at tl7, the effec~ would have been to command the trans-
sponder not to turn on its #l output. By staying high
past tl8, the command is issued to turn on the #l output.
At tl9, the timing circuit recognizes tin this embodiment)
that the #l output should be terminated. The pulse
remains high past t21 and t22, and at time t22 all the
transponders recognize that this extended high pulse
is a reset pulse, and the counters in all the transponders
are thus reset. This description emphasizes the extra-
ordînary amount of information and command signals packed
into a single pulse group in the interactive system of
this invention.
FIGS. l9A-l~F indicate one pulse group of signals
from the controller in FIG. l9A, and the transponder's
response or non-response to each pulse in the group in
FIGS. l9B-lgE. The waveforms in FIGSo 19B-19E depict
the signals at the respecti~e output pins 8 and 1-4 to
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the right of ICl in FIG. 8 and to the xight of output
driver array 135 in FIG. 9. The legend "transmitter"
at the right of FIG. 19 indicates that every time the
waveform in l9B goes high, pin ~ goes high and attempts
to transmit information from the transponder to the
controllerO The other four outputs indicate responses
developed as a functlon of the command information in
FIG. l9A.
In more detail, FIG. l9A shows that at time tO Sl
is closed, and t~e first pulse às initiated. Sl remains
closed until tl, a time duration too short to produce
a response at output pin 1, and at tl switch Sl is
opened. At this time pin 8 goes high and the transponder
attempts to reply, as indicated by pulse 340 in FIG.
l9B. However, at time t2 Sl is again closed to terminate
t~e first command pulse, ana as the controller pulse
goes high the pulse 340 at the transponder is terminated
as shown. Because of the short duration of the first
command pulse, that is, the high portion between tO
and tl, no act;on ~as commanded and there is no change
in the output at pin 1, as depicted by FIG. l9C.
At time t2, switch Sl is closed and remains
closed past the minimun time, shown at t3, required
for a command for output 2 to go high. Accordingly,
the output of pin 2 goes high as shown at the leading
edge of pulse 341 in FIG. l9D. Pul~e 341 is that used
at output pin 2 to turn on LED 81, as already described.
Thus the LED is energized between t3 and t4 while
switch Sl remains closed in the controllex. At t4
switch Sl is opened, pulse 341 i5 ended, and the LED
is deenergized. At this time the transponder attempts
to return information, as shown ~y pulse 342 in FIG.
l~B. However, the time duration between t4 and tS is
too ~rief to allow the return of the ID data, and
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pulse 342 is terminated when switch S1 is again closed
at time t5.
The third pulse in the ~roup of FIG. 19A remains
high for a short period, too brief to command any
action at output pin 3~ Thus the waveform at pin 3
remains low as sh~wn ~y FIG. l9E. At time t6 S1 is
opened and the third pulse goes lo~ as shown in FIG.
l9A, but not as low as the previous lo~s in the pulse
group. This occurs because the third low includes the
time interval during which the ~irst analog voltage is
returned from a connected device. The reduced-ampli-
tude low indicates there is no such device connected
at the transponder then replying. Had there been a
device providing a zero level signal, the third pulse
low would have been at the same level as the previous
lows.
At time t7 Sl is closed to commence the fourth
pulse in the group. The pulse remains high past time
t8, indicating a command to drive output pin 4 high
and effect the corresponding action. In this case the
action is to reset the associated relay, and at time
t8 the leading edge of pulse 343 (FIG. l9F) is generaked
at pin 4 to accomplish this reset. Pulse 343 remains
high until t9, when Sl in the controller is again
opened to terminate the command and at that same time
pulse 343 is also terminated. The fourth low com-
mences at t9, and the extension of this low allows pin
8 to go high and remain high, returning information
from the second analog device, At tlO pin 8 again
3Q goes lowl simultaneousl~ with the transition in the
fourth lo~ as already described, and this condition
remains until tll. At tll the described pulse group
is terminated and the next pulse group is ini~iated.
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From the description in connection ~ith.FIG. 18 and
FIGS. l9A-19F, the flexi~ilit~ o~ the syst~m i.n trans-
mitting commands and recelving information is manifest.
However, those skilled in the art will appreciate that
the system can also transmit other data information,
by regulating the Sl closure time and thus t~e duration
of the controller pulse highs, and also receive ~arious
information from the transponders and/or associated
transducers. One example of such additional data
transmission is evident from considering ~IGS. l9A and
l9D. Because the second pulse remained high for more
than 20 ms (.the preset time in this embodiment~,
represen~ed at t3, the LED was illuminated. Pulse 341
shows the duration of this illumination was about
another 20 ms. Of course, the pulse 341 could have
been shortened, or could have been lengthened beyond
20 ms, to conve~ differen~ information. That is, the
duration of such pulse can itself sig~ify information
eith.er to equipment connected at the transponder, or
to personnel viewing the transpondex operatio~.
Such control of the switch Sl to pass data signals
is depicted in FIGS. 20A-20F. The controller output
pulses in FIG. 20A are again four in number, constituting
a pulse group. The first pulse goes high at time t0
and remains high, with switch Sl closed, past tl, the
minimum time to drive output pin 1 high and commence
data transfer ~y producing the leading edge of pulse
345. This pulse remains high until time t2, when Sl
in the controller is again opened, terminating pulse
345 at time t2. As sh.own this represents a pulse
duration of about I2 ms, which can be a command to
accomplish a certain function or a represen~ation of
an analog value correspond;ng to the pulse time duration.
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At time t2 Sl is opened, and output pin 8 goes
high as the transponder attempts to reply. HDwever,
after only 4 ms switch Sl is again closed, the second
pulse in the transmission group is commenced and the
attempted output of the transponder is terminated as
pin 8 goes low at time t3.
The second pulse remains high as Sl remains closed
past t4, the minimum time to command a function to pass
information to output 2 of the transponder. Thus at
t4 the leading edge of pulse 346 in FIG. 20D is generated,
and this pulse remains high until the controller
switch Sl is again opened, at time t5. This~opening of
Sl terminates pulse 346, and allows pin 8 to go high as
the transponder attempts to reply, but this attempt is
terminated at t6 as switch Sl is closed. Thus the
generation of pulse 346 represents a 32 ms data pulse
forwarded to the addressed transponder.
The third pulse remalns high past t7, at which time
the leading edge of pulse 347 is generated as output pin 3
goes high. The duration of this pulse between t7 and t8
denotes an 8 ms inter~al, and Sl is opened at t8 to terminate
this pulse. The transponder does not attempt to reply
between t8 and t9 because there is no device connected to
supply the analog l signal.
2~ At t9 the fourth controller pulse is initiated as Sl
is again closed, and Sl remains closed past tlO, at which
time output pin 4 goes high and pulse 348 is initiated.
Pin 4 remains high until time tll, when controller switch
Sl is opened to terminate pulse 348 after a 40 ms data trans-
mission. At time tll output pin 8 goes high and the trans-
ponder returns the pulse 350 until time tl2, where the
transition occurs in the fourth low of the pulse group.
This last pulse in the group ends at tl3, at which time the
counters are incremented and t~e next transponder begins
to respond to the pulse group.
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Summary of TechnicaL Advantages
The system of the present invention, by its use
of a bidirectional, interactive communication system
provides many advantages over prior art systems. As
used herein and in the appended claims, a "~idirectional"
communication s~stem~is one in which commands and/or
information are transmitted from a source (controller)
to a receiver (transponder) over a communication path
such as a conductor pair, and data and/or status in-
formation may be selectively transmitted from the
receiver over the same communication path to the
source. The term "interactive" describes a com-
munication system in which command and/or data information
~s included in a pulse group, comprising more than
one pulse, transmitted from the source to the receiver
and, before that one pulse group is terminated,
selected data andjor status information will always
be transm;tted from the receiver to the sourae, until
th~ source terminates the receiver's transmission
with an overriding, simultaneous transmission. The
receiver does not transmit additional pulse(s), but
modifies one ~or more) o~ the source-generated pulses,
and this modification is translated into appropriate
data b~ the source.
The unique, interactive system of this invention
has many important advantages over known arrangements.
Among the more salient features are:
1. Vernier measurement in the controller to
enhance accuracy of the answer signal;
2. Accurate decoding of data from the replying
transponder, even though another transponder may be
malfunctioning at that same time;
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3. Decoding of the answer signal to rec~ver
(1~ data from an associated transducer, ~21 calibration
response information from the replying transponder, ox
(3~ identification data from the repl~iny transponder;
4. Compensation of the transponder and trans~
ducer responses;
5. Automa~ic call for main~enance when extent of
any compensation signal reaches a preset level;
6. Continuous determination of transducer
sensitivity at the controller, which is remote from
the transduc r itself;
7. Use of the transducer sensitivity measurement
in supervising all devices, and determining --- at
the controller --- when alarm and trouble conditions
Occur;
8. Sensitivity adjustment for the remotely located
transducer at the controller, which can be controlled
constantly and automatically (e.g., by a stored
program related to time of day and/or day of week)
or manually (.through a keyboard). The various trans-
ducers can be set to the same, or different, thresholds,
and some or all of th.e transducers can have their
respective thresholds changed at any time;
9. Supply of electrical power to the transponders
and the transducers from the controller, over the same
conductor pair which transfers the data; and
10. Unique supervision of Class A and Class B
systems~
Claim Int~erpretation
A "fire detection" system, as used in the appended
claims, is not limited to a system using ionization
detectors, obscuration detectors, rate of temperature-rise
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detectors, or any o.ther particular detector ype.
Rather it broadly ïncludes systems for detecting
incipient and/or actual combustion.
In the appended claLms the term "connected" means
a d-c connection ~etw~en two components wi.th virtually
zero d-c resistance ~et~een those components. T~e term
"coupled" ~ndicates there is a functional relationship
~et~een two components, with. the possible interposition
of other elements ~etween t~e two components described
as "coupled" or "intercoupled".
While only a particular embodiment of the invention
~as been descri~ed and claimed herein, it is apparent
that various modifications and alterations of the invention
may be made. It is therefore the intention in the
appended claims to cover all such modifications and
alterations as may fall within the true spirit and
scope of the invention.
What is claimed is:
