Note: Descriptions are shown in the official language in which they were submitted.
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A METHOD AND APPARATUS FOR INFREOUENT RADIO
USERS TO SIMPLY OBTAIN EMERGENCY ASSISTANCE
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is related to the following
commonly-assigned Canadian patent applications:
Canadian Application Serial No. 566,664 of Childress
et al, filed May 12, 1988, entitled "Trunked Radio
Repeater System"; Canadian Application Serial No.
566,663 of Childress et al, filed May 12, 1988,
entitled "Failsoft Architecture for Public Trunking
System"; Canadian Application Serial No. 566,660 of
Childress, filed May 12, 1988, entitled "Adaptive
Limiter/Detector Which Changes Time Constant Upon
Detection of Dotting Pattern"; Canadian Application
Serial No. 566,662 of Childress et al, filed May 12,
1988, entitled "Apparatus and Method for Transmitting
Digital Data Over a Radio Communications Channel".
This application is also related to the following
commonly-assigned Canadian patent applications:
Canadian Application Serial No. 580,065 of Nazarenko
et al, filed October 13, 1988, entitled "Processor-to-
Processor Communications Protocol for a Public ServiceTrunking System"; Canadian Application Serial No. 580,097
of Hall et al, filed October 13, 1988 , entitled
"Radio Trunking Fault Detection System"; and Canadian
Application Serial No. 580,064 of Dissosway et al,
filed october 13, 1988, entitled "Mobile Radio
Interface".
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SPECIFICATION
This invention is generally related to the
art of trunked radio repeater systems. The invention
more particularly relates to such repeater systems
using digital control signals transmitted over a
dedicated control channel while also using plural
working channels which are assigned temporarily for
use by individual mobile radio units.
The trunking of radio repeaters is well
known. Early trunking systems used analog control
signals while some more recent systems have utilized
digital control signals. Control signals have been
used on a dedicated control channel and/or on
different ones of the working (voice) channels for
various different reasons and effects. A
nonexhaustive but somewhat representative sampling of
publications and patents describing typical prior art
trunked radio repeater systems is set forth below:
U.S. Patent No. 3,292,178 - Magnuski (1986)
U.S. Patent No. 3,458,664 - Adlhoch et al (1969)
U.S. Patent No. 3,571,519 - Tsimbidis (1971)
U.S. Patent No. 3,696,210 - Peterson et al (1972)
U.S. Patent No. 3,906,166 - Cooper et al (1975)
U.S. Patent No. 3,936,616 - DiGianfilippo (1976)
U.S. Patent No. 3,970,801 - Ross et al (1976)
U.S. Patent No. 4,001,693 - Stackhouse et al (1977)
U.S. Patent No. 4,010,327 - Kobrinetz et al (1977)
U.S. Patent No. 4,012,597 - Lynk, Jr. et al (1977)
U.S. Patent No. 4,022,973 - Stackhouse et al (1977)
U.S. Patent No. 4,027,243 - Stackhouse et al (1977)
U.S. Patent No. 4,029,901 - Campbell (1977)
U.S. Patent No. 4,128,740 - Graziano (1978)
U.S. Patent No. 4,131,849 - Freeburg et al (1978)
U.S. Patent No. 4,184,118 - Cannalte et al (1980)
U.S. Patent No. 4,231,114 - Dolikian (1980)
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U.S. Patent No. 4,309,772 - Kloker et al (1982)
U.S. Patent No. 4,312,070 - Coombes et al (1982)
U.S. Patent No. 4,312,074 - Pautler et al (1982)
U.S. Patent No. 4,326,264 - Cohen et al (1982)
U.S. Patent No. 4,339,823 - Predina et al (1982)
U.S. Patent No. 4,347,625 - Williams (1982)
U.S. Patent No. 4,360,927 - Bowen et al (1982)
U.S. Patent No. 4,400,585 - Kaman et al (1983)
U.S. Patent No. 4,409,687 - Berti et al (1983)
U.S. Patent No. 4,430,742 - Milleker et al (1984)
U.S. Patent No. 4,430,755 - Nadir et al (1984)
U.S. Patent No. 4,433,256 - Dolikian (1984)
U.S. Patent No. 4,450,573 - Noble (1984)
U.S. Patent No. 4,485,486 - Webb et al (1984)
U.S. Patent No. 4,578,815 - Persinotti (1985)
Bowen et al is one example of prior art
switched channel repeater systems which avoid using a
dedicated control channel -- in part by providing a
handshake with the repeater site controller from a seized
"idle" working channel befsre communication with a called
unit(s) is permitted to proceed.
There are many actual and potential
applications for trunked ratio repeater systems.
However, one of the more important applications is for
public service trunked (PST) systems. For example, a
single system of trunked radio repeaters may be
advantageously used by an entire metropolitan area to
provide efficient radio communications between individual
radio units within many different agencies. Each agency
may, in turn, achieve efficient communication between
individual units of different fleets or subunits (e.g.,
the police department may have a need to provide
efficient communications between different units of its
squad car force, different portable units assigned to
foot patrolmen, different units of detectives who are
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narcotics agents, and the like). Sometimes it may be
important to communicate simultaneously with
predefined groups of units (e.g., all units, all squad
cars, all foot patrolmen, etc.). At the same time,
other agencies (e.g., the fire department, the
transportation department, the water department, the
emergency/rescue services, etc.) may be in need of
similar communication services. As is well known to
those familiar with trunking theory, a relatively
small number of radio repeaters can efficiently
service all of these needs within a given geographical
area if they are trunked (i.e., shared on an
"as-needed" basis between all potential units).
The potential advantages of trunked radio
repeater systems for public services is so well
recognized that an organization known as the
Association of Public-Safety Communications Officers,
Inc. (formerly the Association of Police
Communications Officers) (APCO) has developed a set of
highly desirable features for such a system commonly
known as the "APCO-16 Requirements." A complete
listing and explanation of such requirements may be
found in available publications known to those in the
art.
An advantageous trunked radio repeater
system is described in the aforementioned Canadian
Application Serial No. 566,664 of Childress et al.
That application describes a trunked radio repeater
system architecture in which the RF "control shelf"
which receives and transmits radio frequency signals
for a particular working or control channel is
controlled by a microprocessor-based "trunking card"
(hereafter referred to as a "GETC" -- General Electric
Trunking Card) which performs the signal processing
functions associated with the control shelf and RF
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channel. A primary site controller (e.g., a
minicomputer) is connected to various trunking cards,
and receives digital signals from and sends digital
signals to the various trunking cards. The primary
site controller performs the control functions of the
system (during normal system operations) -- and thus
performs tasks such as call logging, dynamic
regrouping, and "patch" coordination as well as other,
more route control functions such as assigning
channels to new calls. One or more dispatch consoles
also connected to the primary site controller generate
messages controlling the primary site controller and
also monitor the status of the entire system via
messages sent to it from the site controller.
Not so long ago, mobile radio transceiver
installations were limited to a trunk-mounted mobile
radio transceiver unit connected via a multiple
conductor cable to a dashboard-mounted control head.
The control head was typically relatively simple,
including only an ON-OFF switch, a volume control, a
microphone with associated PTT (push to talk) and hook
switches, a speaker, receiver/transmit indicator
lamps, and a channel selector switch.
The channel selector switch was hard-wired
for specific crystal-controlled frequencies, and the
transceiver always transmitted and received on the
same set of frequencies (e.g., a set of frequencies
dedicated to emergency communications and always
monitored by an emergency dispatch operator) when the
channel selector switch was switched into a given
position. Users typically would adhere mnemonic
labels on the control head itself adjacent to channel
switch positions to help them remember which channels
were which, or refer to a table of channel allocations
attached to the vehicle dashboard. Such radios were
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relatively simple to operate even by unsophisticated
users.
Significantly, RF channels typically are not
used to select desired call participants in modern
digitally trunked radio repeater systems. In past
systems, for example, all police dispatcher might
normally monitor "channel 1", so that a user wishing
to control the police dispatcher needed only to
transmit on channel "1". In some radio services
(e.g., the 27 mHz Citizen's Band, the low frequency
and VHF marine bands, and the aviation radio bands),
specific operating frequencies have been set aside
exclusively for emergency communications use. For
example, by law, Citizen's Band channel 9 (a frequency
around 27.1 mHz) can be used only for emergency
communications, and many police stations and other
public service agencies throughout the country monitor
this frequency. To make an emergency call using a
Citizen's Band transceiver, a user tunes to channel 9
and transmits.
Modern "digital" mobile radio transceivers
(i.e., transceivers controlled by microprocessors) are
not limited to the crude control functions provided in
mobile radio transceivers of the past. For example,
modern digital radio transceivers include much
internal digital control circuitry (e.g.,
digitally-controlled frequency synthesizers, digital
displays, etc.). Transceiver operating frequencies
are now controlled by digital frequency synthesizers
in response to user selections made via control head
push buttons or knobs.
Typically, all mobile transceivers in a
digitally trunked radio communications system monitor
a digital control channel when they are not engaged in
actual communications. Transceivers are identified by
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"group" and "individual" identification codes (long
digital data strings). When a transceiver detects a
"working" channel assignment message which specifies a
transceiver "group" or "individual" identification
code it is a member of, the transceiver ceases
monitoring the RF control channel and changes
frequency to the "working" channel -- where it
participates in communications. After the
communications end, the transceiver ceases operating
on the working channel and reverts back to monitoring
the control channel.
If a mobile radio user in such a digitally
trunked radio communications system wishes to contact
another transceiver or a dispatcher, the user controls
his transceiver to transmit a channel assignment
request message on the control channel, this channel
assignment request message specifying the group or
individual identification code of the transceivers) he
wishes to contact. The repeater system responds by
transmitting a channel assignment message directing
the calling transceiver and all of the transceivers
the user wishes to contact onto a working channel
frequency where communications is to take place.
Needless to say, it would be too much to
expect users to remember and key in the group and
individual identification codes of parties they wish
to call. Accordingly, modern digital radio
transceivers include internal preprogrammed EEPROM
memory devices which store tables of group and
individual identification codes and associate entries
in those tables with corresponding positions of a
group/individual call selector switch(es). When the
user operates the selector switch, his transceiver
automatically reads a corresponding entry from the
internal memory device and thus obtains an individual
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or group identification code. The transceiver then
automatically transmits the code so obtained to the
repeater station over the system RF control channel
with a channel assignment request message.
From a user standpoint, then, selection of a
group or individual using the selector switch is the
equivalent to selecting a ~channel" on a radio
transceiver of the past. Nevertheless, operating a
modern digital transceiver of this type can be a
difficult and challenging experience to an
unsophisticated user. With digital transceivers now
being installed where radios never were present before
(e.g., in city and county service vehicles such as
garbage trunks, school buses and the like), a large
number of people who never used radio communications
before are now being provided with such
communications. Such users are unsophisticated in and
unknowledgeable about radio communications in general,
and many of them find using a modern digital radio
transceiver to be a trying experience.
The present invention provides a digital
mobile radio transceiver which allows even the most
unsophisticated user to simply and easily obtain
emergency communications. The transceiver is
programmed with "personality" data specifying one or
more "system", each "system" specifying one or more
"groups" of or individual radio transceivers. For
example, a police radio might be programmed with a
first "system" specifying groups of and individual
police radio units, and a second "system" specifying
groups of and individual fire radio units. Each
system is identified by a one or two digital number
(e.g., l-N), and each group is identified with a one
or two digit number (e.g., l-M). Systems are selected
by operating a first selector switch, and groups are
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selected by operating a second selector switch. The
transceiver simultaneously displays the "group" and
"system" which have been selected.
The repeater system includes one or more
group identification codes which uniquely designated
an emergency communications handler (e.g., an
emergency dispatch operator). The group designated by
the group selector switch position "9" of each system
programmed into the radio transceiver corresponds to
this emergency group identification code. Moreover,
the "system" designated by system selector switch "11"
has only one "group" -- the emergency group
identification code corresponding to the group
selector position "9".
In the preferred embodiment, the transceiver
displays selected "group" first and selected "system"
second. Whenever the user operates the selector
switches to select the group "9" and the system "11"
(causing the transceiver to display "911"), the
emergency group identification code is selected.
Similarly, whenever the user selects group "9" and any
system, the emergency operator is selected; and
whenever the user selects system "11", he can only
select group "9" corresponding to the emergency
operator.
Since users typically associate both the
number "9" alone and the number "911" with emergency
communications from their experiences with Citizen's
Band radio and telephone number conventions), they do
not need to remember any new special codes in order to
use the radio transceiver provided by the present
invention to reach an emergency operator. Moreover,
the user only needs to select either group "9" or
system "11" in order to reach an emergency operator --
making it very easy for even unsophisticated users to
1 ~27'~9
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obtain emergency communications.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages of
the present invention will be better and more
completely understood by referring to the following
detailed description of presently preferred exemplary
embodiments in conjunction with the appended sheets of
drawings, of which:
FIGURE 1 is a schematic block diagram of an
overall trunked radio repeater system 100 of the
present invention;
FIGURE 2 is a perspective view of the mobile
radio transceiver control head shown in FIGURE 1;
FIGURE 3 is a more detailed block diagram of
the mobile radio transceiver and control head; and
FIGURE 4 is a flow chart of exemplary
program control steps performed by the transceiver
microprocessor shown in FIGURE 3.
DETAILED DESCRIPTION OF PRESENTLY
PREFERRED EXEMPLARY EMBODIMENTS
OVERALL SYSTEM ARCHITECTURE
An exemplary trunked radio repeater system
100 in accordance with this invention is generally
depicted in FIGURE 1. System 100 includes at least
one (and typically many) mobile (or portable) radio
transceiving stations 150 and an RF repeater station
175. Mobile transceiving station 150 communicates via
an RF link and repeater station 175 with other mobile
transceiving stations and/or with landbased parties
connected to the repeater station by conventional
dial-up landlines.
Repeater station 175 includes a site
controller 410, individual repeater channel
transceivers 177, and a multiplexing telephone
interconnection network ("switch", or "MTX") 179.
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Site controller 410 is preferably a mainframe digital
computer which oversees the general operation of
repeater station 175. In particular, site controller
410 controls the operation of RF transceivers 177 by
transmitting digital signals to and receiving digital
from "trunking cards" ("TC") 400 connected between the
site controller and individual transceivers (although
only one transceiver 177 and one trunking card 400 are
shown in FIGURE 1, there typically are many such
trunking card/transceiver combinations in repeater
station 175 -- one for each RF channel the repeater
station operates on.
Site controller 410 communicates with one or
more dispatch consoles 102 via a "downlink" 103 which
includes a "downlink" trunking card 450 and a "switch"
trunking card 454. The downlink 103 also typically is
channeled through switch 179. Also connected to
switch 179 are AVL (automatic vehicular locating
system) 181 and CAD (computer aided dispatch system)
183. A system manager console/computer station 416 is
connected to site controller 410 and to switch 179 to
allow a system manager to oversee and control the
overall operation of system 100.
A remote receiver 187 and associated
concentrator/voter 189 may be connected to trunking
card 400 to allow so-called "RSSI" signal strength
measurements to be based on the stronger of the signal
level received at the central repeater station site
and the signal level received at a remote site --
thereby increasing the reliability of suchmeasurements.
An RF link ("RF") connects RF transceivers
177 with mobile transceiving stations 150. Mobile
station 150 is capable of transmitting digitized voice
or digital data signals (encrypted or unencrypted) to
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and receiving such signals from repeater station 175
over the RF link.
In the configuration shown in the upper
left-hand portion of FIGURE 1, mobile station 150
includes a mobile RF transceiver 152 connected to a
control head 154 via a serial digital bus 153. Mobile
transceiver may also be connected to a vehicular
repeater 156 via the serial bus. A mobile data
terminal interface 158 may connect the serial bus to a
mobile data terminal (MDT) 162. A separate digital
voice guard module 164 performs data encryption and
decryption on digitized voice and/or digital data
signals using the conventional DES algorithm.
In the alternate mobile radio configuration
shown in the lower left-hand corner of FIGURE 1, a
coupler 166 is used to connect dual control heads
154A, 154B to serial bus 153. In this configuration,
a mobile data terminal 162 and associated interface
158 may be connected directly to serial bus 153 and/or
to bus 153A (on the output of the coupler 166). Voice
guard module 164 is preferably connected to bus 153A
when dual control heads 154A, 154B and associated
coupler 166 are used.
As illustrated, individual radio units
(mobile or portable radio transceivers) of various
groups communicate with one other (both within and
possibly outside of their own groups) via shared radio
repeater channels. A dispatch console 102 supervises
the operation of repeater system 102. There may be
multiple dispatch consoles 102 (one for each separate
fleet of mobile/portable units) and a master or
supervisory dispatch console for the entire system if
desired.
OVERALL DESCRIPTION OF MOBILE TRANSCEIVER 152
The 16-PLUS MOBILE RADIO TRANSCEIVER 152
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used in the preferred embodiment is a microprocessor-
controlled digital radio transceiver having a variety
of advanced functions and using the RF signalling
protocol described in the aforementioned Canadian
Application Serial No. 566,664 of Childress et al.
FIGURES 2 and 3 show transceiver 152 and
control header 154. Transceiver 152 includes
microprocessor 470 (an 8031 microprocessor in the
preferred embodiment), and including internal or
external read only memory and random access memory
device 471 storing "personality" data specifying
parameters of repeater systems 100 mobile transceiver
152 is authorized to access (and also storing program
control instructions which control the microprocessor
to perform predetermined control tasks under software
control~. Transceiver RF circuits 474 receive RF
signals from an antenna 476, demodulate those RF
signals to extract the intelligence they carry, pass
resulting received analog signals to analog circuits
478, and pass received digital signals to the
microprocessor 470. RF circuits 474 similarly
received digital signals from microprocessor 470 and
analog signals from analog circuits 478, produce an RF
signals, modulate the RF signal with these analog and
digital signals, and transmit the modulated RF signals
(after amplification) to the repeater station via
antenna 476.
The structure and operation of analog
circuits 478 and RF circuits 474 are conventional and
well understood by those skilled in this art.
Briefly, analog circuit 478 include an audio
multiplexer which selects between various audio inputs
(e.g., the audio produced by a control head
microphone, decrypted voice guard audio information
provided by a voice guard module, receiver audio
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provided by RF circuits 474, an alert tones provided
by microprocessor 470). Analog circuits 478 also
include a summing device which sums the selected audio
input with various digital signals provided by
microprocessor 470, a level adjusting circuit which
adjusts the level of the summed analog signal, and
various amplifier/limiter stages which prepare the
level-adjusted signal for sue by RF circuits 474 to
modulate the RF carrier and/or for application to
control head speaker. RF circuits 474 include a
conventional digitally-controlled frequency
synthesizer 480 controlled by digital data signals
produced by microprocessor 470 and conventional RF
transmitting and receiving circuitry (e.g., an
intermediate frequency "strip" connected to an FM
demodulator/detector, and an RF transmitter and
associated modulating and RF amplifier stages).
Control head 154 includes its own
microprocessor, a digital data "group" display 556, a
digital data 'system" display 560, a keyboard 558, a
"group" selector switch 562 and a "system" select
switch 564. Control head 154 is connected to
transceiver microprocessor 470 via a 3-wire serial
data bus 153. Audio lines 562 connect control head
microphone 550 and control head speaker 552 to
transceiver analog circuits 478.
Referring now more particularly to FIGURE 3,
EEPROM 471 (which is preferably programmed at the time
mobile transceiver 152 is installed in the field using
a conventional "suitcase" programmer) contains
"personality" digital data defining the operation of
the transceiver (e.g., operating RF frequencies, and
identification codes of groups of and individual radio
transceivers the programmed receiver is authorized to
contact). Each transceiver 152 is preprogrammed to
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recognize an individual transceiver identification
code uniquely corresponding to it. In addition,
transceiver 152 is preprogrammed to recognize itself
as being a member of one or more logical "groups" of
radio transceivers.
Transceiver EEPROM 471 stores a plurality of
system data blocks 600, each data block including a
frequency table 602 and a group table 604. System
blocks 600 correspond to (a) different logical
collections of groups of and/or individual radio
transceivers, (b)) different repeater sites, or (c)
both.
Frequency tables 602 store channel numbers
and associated frequencies of a plurality (typically
20) of RF channels a specific repeater site operator
on. Group tables 604 include a plurality of group
records 606. Each group record 606 contains a group
number field 608 (corresponding to the number
displayed on control head group display 556 when the
group record is selected), and an identification code
field 610 (which uniquely identifies the corresponding
group of or individual transceivers with a digital
identification code). System blocks 600 are, like
group records 606, uniquely numbered (e.g., l-N),
these numbers corresponding to the number displayed on
control head system display 560 when the system is
selected.
Transceiver EEPROM 471 may be programmed to
permit contact with the same groups of or individual
radio transceivers via different radio repeater
sites. These different sites are selected by the
"system" selection switch 564 in the preferred
embodiment. Typically, different sites will have
different radio channels frequencies allocated to them
(so that the sites can be geographically proximate to
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one another and yet operate simultaneously on a
non-interfering basis). In such case, EEPROM 471
would include several data blocks 600, each block
containing identical group tables 604 but containing
different frequency tables 602, the different
frequency tables specifying the RF channel frequencies
of corresponding different radio repeater sites.
EEPROM 471 may also be programmed to contact
different collections of groups of and/or individual
radio transceivers, these different collections also
being specified by different "system." For example, a
police radio might be programmed to contact other
police radios when operating in "system 1," to contact
county service vehicles when operating in "system 2, n
and to contact fire services when operating in "system
3." EEPROM 471 of such transceivers would include
different system data blocks 600 corresponding to
different collections of groups of and/or individual
radio transceivers. If the same repeater site were to
be used for each different collection, the frequency
tables 602 of the various system data blocks 600 would
all be identical, but the group tables 604 would
differ.
Although FIGURE 3 shows group number fields
608 being explicitly stored, they need not be. For
example, microprocessor 470 preferably includes a
selected group register 620 which is loaded with the
numerical designation of a group selected by group
selector switch 562; and a selected system register
622 containing the numerical designation of a system
selected by system selector switch 564. The contents
of selected group register 620 is displayed on control
head group display 556, and is also used to "point" or
"index" a group record 606 within the selected system
data block 600. Similarly, the contents of selected
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system register 622 are displayed on control head
system display 560, and are also used to index one of
system data blocks 600 stored in EEPROM 471. Hence,
the combination of the setting of group selector
switch 562 and the setting of system selector switch
564 uniquely specifies both a system data block 600
and a group record 606 within the selected system data
block.
In addition, although FIGURE 3 shows system
data blocks 600 each including an explicitly stored
frequency table 602 and an explicitly stored group
table 604, the preferred embodiment actually stores
each unique frequency table only once and each unique
group table 604 only once, and then stores addresses
or other designations of the frequency and group
tables in system data blocks 600. This database
structure avoids the need to store multiple identical
copies of the same frequency tables and multiple
identical copies of the same group tables 604 in
EEPROM 471 (since different systems typically use the
same frequency table with different group tables; and
different systems typically use the same group table
with different frequency tables).
In the preferred embodiment, system data
blocks are designated by integers 1-N. The system
data block 600 (11) is a reserved system block which
includes only one "valid" group record 606 in its
group table 604 -- a record corresponding to group
number "9". Preferably, system data block 600 (11)
frequency table 602 contains the RF channel numbers
- and corresponding frequencies for the repeater site
the user of radio transceiver 152 is most likely to
use. All of the other group records 606 stored within
system data block 600 (11) group table 604 specify
'invalid" (e.g., all zeros) group identification codes
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except for group record (9), which contains the
identification code corresponding to the emergency
dispatch operator. Transceiver microprocessor 470
prevents a user from selecting a group record 606
containing an invalid identification code -- and
forces selected group register 620 (and thus also,
control head group display 556) to contain a group
number corresponding to a record storing a valid code.
Whenever system selector switch 564 is
rotated to select system number 11 (i.e., to select
system data block 600 (11), transceiver microprocessor
470 examines the group records in the selected system
data block, and finding that all of the records except
for the one corresponding to group number 9 contain
invalid group identification codes, forces selection
of group record 604 (9) and forces control head group
display 556 to display the number "9". The group
identification code field 610 (9) of this selected
group record 606 contains an identification code of an
emergency dispatch operator or other emergency radio
unit.
Consequently, whenever the user selects
system number 11, emergency group number 9 is
automatically selected, the number "9" is displayed on
control head group display 556, and transceiver 152
initiates a call to the emergency dispatch operator
when the user then depresses the microphone
push-to-talk button.
Regardless of the nature of the groups
specified in group table 604 of system data blocks 600
other than system data block 600 (11), the group
record 606 (9) in each and every system data block 600
stored in EEPROM 471 has an identification code field
610 containing the identification code of that same
emergency dispatch operator. No matter which system
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data block 600 is selected by select system register
622, select group register 620 selects a group record
606 (9) containing the identification code of the
emergency dispatch operator whenever the user selects
group number "9".
Transceiver 152 thus permits a user to very
easily establish communications with the emergency
dispatch operator. Whenever the user selects group
number "9" (an easy-to-remember number which the user
probably already associates with emergency
communications because of its citizen's Band
connotations), transceiver 152 selects the
identification code corresponding to the emergency
dispatch operator. Similarly, whenever the user
selects system number '11", transceiver 152
automatically selects group number "9", displays the
combined group/system designation "911" (see FIGURE 2)
-- which the user no doubt already associates with
emergency communications from its telephone system
connotations -- and similarly selects the
identification code of the emergency dispatch
operator.
FIGURE 4 is a flowchart of exemplary program
control steps performed by transceiver microprocessor
470 in the preferred embodiment to select a group
identification code and set of operating frequencies
in response to user operation of control head switches
562, 564.
Nicroprocessor 470 first obtains the current
control head group selector switch 562 and system
selector switch 564 settings from the control head
154 (e.g., by transmitting messages over serial data
bus 153), and loads those settings into microprocessor
select group register 620 and select system register
622, respectively (block 650). Microprocessor then
1~2~i9
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attempts to use the contents of select group register
620 to index a system data block 600 stored in EEPROM
471 Iblock 652). If no system data block exists in
EEPROM 471 which corresponds to the contents of select
system register 622, microprocessor 470 overwrites the
contents of select system register with a designation
of a system data block which does exist (e.g., system
data block "1") (block 654).
Microprocessor 470 then determines whether
the selected system data block 600 includes a group
record 606 corresponding to the group number stored in
select group register 620 which has a valid group
identification code in its ID code field 610 (block
656). If the selected group record does not contain a
valid identification code in its ID code field 610,
microprocessor 470 overwrites the contents of select
group register 620 with the group designation of a
group record in the selected system data block which
does contain a valid id code (block 658). For
example, if select system register 622 selects system
data block 600 (11), microprocessor 471 overwrites the
contents of select group register 620 with a
designation of group record 606 (9) regardless of the
setting of group selection switch 562 -- since system
data block 600 (11) contains only one group record
having a valid identification code (i.e., the code
corresponding to the emergency dispatch operator).
Microprocessor 470 then displays the
contents of select group register 620 on control head
group display 556, and displays the contents of select
system register 622 on control head system display 560
(e.g., by sending appropriate messages to the control
head 154 over serial data bus 153) (block 660).
Microprocessor 470 meanwhile reads the group
identification code from field 610 of the selected
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group record 606 in the selected system data block 600
(block 661), loads the frequency table 602 of the
selected system data block for use in controlling
frequency synthesizer 480 (block 662), and loads the
read group identification code into an internal
register in preparation for transmitting it within a
channel assignment request message over the system RF
control channel (specified by the loaded frequency
table data) upon depression by the user of a
microphone push-to-talk switch (block 664).
While the invention has been described in
connection with what is presently considered to be the
most practical and preferred embodiments, it is to be
understood that the invention is not to be limited to
the disclosed embodiments, but on the contrary, is
intended to cover various modifications and equivalent
arrangements included within the spirit and scope of
the appended claims.
