Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: ALARM PANEL PROTOCOL CONVERTER
FIELD OF THE INVENTION
The present invention relates to an alarm panel
circuit connected to an alarm panel providing a signal
conversion arrangement allowing communications between an
alarm panel using one communications protocol and a
receiver using a different protocol.
BACKGROUND OF THE INVENTION
Generally, alarm panel systems detect and announce
various conditions, such as a motion sensed, glass broken,
or a door opened for the monitored premises. Some security
applications require a high degree of security and
sophisticated alarm panels communicate the system state via
specialized dedicated comml]n;cation lines to a receiver
located at the initial switching station. These panels are
~hard-wired~ to the receivers. Typically, a receiver is
connected to a number of alarm panels and sequentially
polls each panel for their status. In response, each panel
will reply with a message indicating either that there are
no alarm conditions or that a sensor (or sensors) connected
to the panel is reporting an alarm condition or other
condition.
A receiver must meet m;niml]m statistical standards
to obtain certification. Therefore, a receiver must be
able to answer calls from any of its connected alarm panels
with a m;n;ml]m statistical degree of certainty. To achieve
this statistical certainty, dedicated data links between
alarm panels and a receiver may be used. The statistical
certainty of such a configuration is primarily based on the
communications traffic density of the data links.
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In Canada, the telephone company provides dedicated
data links connecting individual alarm panels to a receiver
at the telephone switching station. The receiver and the
alarm panels communicate with the receiver using a data
link protocol known as Digital Voice Access Service (DVAC).
This arrangement requires a new line being provided for
each installation and is quite expensive to install and
maintain.
An alarm system can use conventional telephone
lines as a communications link between alarm panels and the
receiver but this is considered less secure and would
require new alarm panels.
There are many existing alarm panels which use the
DVAC protocol and these alarm panels typically are
associated with a sophisticated group of sensors. This
further complicates any changes which involve replacing the
alarm panel. Frequency based protocols have been developed
which enable communications between the alarm panel and the
receiver over the telephone network whether or not the line
is already seized. For applications requiring a higher
degree of security, a dedicated telephone line can be
provided. With a dedicated telephone line, the response
time is faster and security is improved. With a dedicated
telephone line, the security system is statistically
deterministic, like alarm panel systems using dedicated
data links. One particular protocol uses Frequency Shift
Keyed ("FSK") tones; another protocol uses an encoded
"spread spectrum" protocol which disperses the content of
the message through a range of frequencies; another
protocol uses a series of low frequency signals. Signals
coded using these frequency based protocols are generally
not audible to the telephone users or non intrusive.
Unfortunately, alarm panels using the DVAC protocol
cannot use the standard telephone lines and a frequency
based communications protocol. Wiring complications make
installation of a new alarm panel impractical. As such,
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alarm panels which use a dedicated data link and a data
link are difficult to convert to a system using the
telephone network and a frequency based protocol.
The present invention overcomes these limitations
by providing an alarm panel conversion unit which converts
signals from a data link protocol to a frequency based
protocol for the telephone network and vice versa. A
frequency based protocol receiver is located at the
telephone switching station.
As such, the panel conversion unit provides an
alarm panel conversation circuit. All signals from the
alarm panel are received by the conversion unit using the
DVAC protocol. The unit provides the appropriate DVAC
signals to the alarm panel. The alarm panel communicates
solely with the conversion unit. The conversion unit
produces the query signals sent to the alarm panel and
receives the response signals from the alarm panel. The
conversion unit extracts information of the status of the
system from the responses and generates a frequency based
protocol alarm panel status signals. Finally, when the
frequency based protocol receiver queries the conversion
unit, the conversion unit sends the frequency based
protocol status message over the telephone network to the
receiver.
SUMMARY OF THE INVENTION
A converter for an alarm panel according to the
present invention comprises a first receiver and
transmitter for connecting to an alarm panel and
comml]n;cate therewith according to a DVAC protocol for
extracting alarm system status signals, a conversion
arrangement for converting alarm system status signals from
a DVAC protocol to a frequency based protocol, and a second
receiver and transmitter for communicatin~ over a telephone
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system with a receiver using a frequency based telephone
protocol.
According to an aspect of the invention, the first
receiver and transmitter sends a DVAC query signal on a
predetermined basis.
According to a further aspect of the invention, the
conversion arrangement includes a look up table of DVAC
alarm panel signals and corresponding frequency based
signals which is used to convert system status signals from
DVAC protocol to frequency based protocol.
According to an aspect of the invention, the converter
uses a spread spectrum protocol, a frequency shift key
protocol or a low frequency based protocol.
The present invention is also directed to the
combination which includes an alarm panel which transmits
status signals using a DVAC protocol and processes received
DVAC protocol signals, a converter immediately adjacent
said alarm panel which receives the alarm panel status
signals and converts the status signals to an equivalent
frequency based protocol status signal and provides a
suitable DVAC response signal to the alarm panel. The
converter further includes a second receiver and
transmitter for communicating over a telephone system with
a remote receiver connected thereto by the telephone
system. The second receiver uses a frequency based
telephone protocol to report the alarm panel status when a
query signal is received from said remote receiver.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiments of the invention are
shown in the drawings, wherein:
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Figure 1 is a schematic of a prior art security
system including a central panel utilizing a data
connection to the telephone office;
Figure 2 is a schematic of a security alarm panel
of the present invention including a DVAC alarm panel
connected to a converter for DVAC and frequency based
protocol signals, and a connection to a frequency based
protocol scanner at the telephone office; and
Figure 3 is an expanded schematic of the present
invention and the communication arrangement of an alarm
panel.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 shows details of a prior art panel system
1 using a DVAC comml]n;cations system. Sensors 3 are
connected to DVAC alarm panel 2. Alarm panel 2 is
connected to DVAC modem 4 through Tx data and Rx data F1
and F2 subsets 5 and 6 respectively. Modem 4 is connected
through a dedicated telephone data connection 7 to DVAC
receiver 8, located at the Telephone Switching Office 10.
The DVAC communications system operates as follows.
The state of all sensors are detected by alarm panel 2.
Meanwhile, receiver 8 intermittently polls alarm panel 2
for the status of sensors 3 through data connection 7, DVAC
modem 4 and terminals F1 and F2. Typically, alarm panel 2
is polled two or three times every minute. In response to
each polling, alarm panel 2 sends a DVAC signal through Tx
data and Rx data terminals indicating the status of the
sensors. Receiver 8 accepts and interprets any and all
responses received from alarm panel 2 on line 7. If a
response indicates an alarm condition, receiver 8 notifies
the central security office through switch 9. If the alarm
panel fails to respond to a query, this provides an
indication that an alarm condition exists.
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Figure 2 shows details of the present invention
wherein modem 4 and receiver 8 of Figure 1 are replaced by
a signal converter 18 and frequency based protocol scanner
23, respectively. The invention operates as follows.
Sensors 17 are connected to alarm panel 16. Converter 18
intermittently polls alarm panel 16 through Tx data and Rx
data terminals using the DVAC protocol. The rate of polling
used by the converter 18 can be several times more frequent
than the typical polling rate used by a DVAC receiver, as
the converter is only polling a single panel. In response
to each polling, alarm panel 16 sends a DVAC signal through
Tx data and Rx data indicating the status of the sensors.
All signals between alarm panel 16 and converter 18 are
DVAC signals. The alarm panel 16 continues in its normal
operation and is merely polled more frequently by the
converter 18. Therefore the alarm panel 16 and the sensors
17 remain unchanged but now essentially report to converter
18.
Scanner 23 periodically queries converter 18 for
the status of the alarm system. All commllnl cations between
scanner 23 and converter 18 uses a frequency based
protocol. Converter 18 receives and converts the status of
the alarm panel 16 for reporting to scanner 23 when scanner
23 polls the converter or otherwise requires converter 18
to report. In this way, the converter acts as an
intermediary and provides appropriate translation to allow
DVAC control panel 16 to report to scanner 23 using a
frequency protocol and telephone line 21 and without the
specialized date link 7 of Figure 1.
Converter 18 to scanner 23 appears to be an alarm
panel which uses a frequency based protocol. Converter 18
to alarm panel 16 appears to be a scanner which uses the
DVAC protocol.
Figure 3 shows aspects of the converter 34.
Converter 34 contains microprocessor 35 and Digital Signal
Processor (DSP) 36. Microprocessor 35 is the main
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controlling unit of converter 34. In response to a polling
signal sent by the converter to the alarm panel, the
converter receives system status signals. These signals
are processed by microprocessor 35. It extracts the system
status information received in the signals from the alarm
panel and then accesses protocol look-up table 38 to select
an equivalent frequency based protocol system status
signal. Finally, when scanner 39 sends a query to
microprocessor 35, DSP 36 generates and sends an equivalent
frequency based protocol system status signal to scanner
39.
With this arrangement, existing alarm panels which
operate using the DVAC protocol are maintained thereby
avoiding costly rewiring. The alarm panel now reports to a
converter located on the premise over its own data link.
The frequency of polling is increased. The converter
receives and processes signals received from the alarm
panel and converts the signals into an equivalent frequency
based signal. This equivalent signal indicating the
present status of the alarm system is provided to the
scanner in response to a query signal provided over a
telephone line. The security level of the system is
maintained while the costs for the communication link has
been reduced.
The frequency based protocol includes spread
spectrum protocol and frequency shift key protocol as two
examples. The frequency range is preferrably in the range
of 20 hz to 6000 hz.
From the above, it can be appreciated that the
converter can be modified to report in any desired manner
or protocol to a remote scanner. The alarm panel continues
to function as if its operation has not changed.
Although various preferred embodiments of the
present invention have been described herein in detail, it
will be appreciated by those skilled in the art, that
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variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
