Multiple sensor intrusion detection system

• US 4,321,592 A
• Filed: 05/30/1978
• Issued: 03/23/1982
• Est. Priority Date: 05/30/1978
• Status: Expired due to Term

• Current Assignee: Sentrol Incorporated (Carrier Global Corporation)
• Original Assignee: American District Telegraph Company (Johnson Controls International plc)
• Inventors: Crandall, Richard E., Galvin, Aaron A., Apsell, Sheldon P.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Nowicki, Joseph E.
• Application Number:
  US05/910,534
• Time in Patent Office: 1,393 Days
• Field of Search: 340/505, 340/506, 340/504, 340/518, 340/521, 340/524, 340/531, 340/538, 340/541, 340/536
• US Class Current: 340/541
• CPC Class Codes: G08B 13/00 Burglar, theft or intruder alarms
• CPC Class Codes: G08B 25/014 Alarm signalling to a central station with two-way communication, e.g. with signalling back
• CPC Class Codes: G08B 25/04 using a single signalling line, e.g. in a closed loop

Abstract

A multiple zone intrusion detection system in which a plurality of intrusion sensors can be readily converted into the system without system modification, and in which mode control signals from a central control unit and alarm signals from the sensors are both conveyed on a single conductor of the system cable. Each sensor has an associated interface module which permits coupling of different types of sensors to the system and sharing of a single conductor for mode control signals and alarm signals.

Claims

1. An intrusion detection system comprising:

a control unit coupled to a multi-conductor cable extending along a predetermined path in a facility to be protected;

a mode selector coupled to said control unit and providing mode control signals which are at respective signal levels corresponding to selected display modes of sensor indicators for control of the operating display mode of the sensor indicators;

one or more intrusion sensors associated with the sensor indicators and connected to said cable and operative to provide an alarm signal upon intrusion detection;

alarm means coupled to said control unit and operative to denote an alarm condition detected by one or more of said intrusion sensors;

for each of said sensors, an interface circuit coupling its sensor to said cable and operative in response to the mode control signals received on one line of said cable from said control unit to determine the display mode of the sensor indicator, and operative in response to alarm signals from said sensor to convey an alarm signal on the same line of said cable to said control unit for actuation of said alarm means irrespective of the selected display mode of the sensor indicator specified by the mode control signals.

2. The system of claim 1 including a zone indicator coupled to said sensors and operative to provide an indication of the zone in which an intrusion detection has occurred.

3. The system of claim 1 wherein said intrusion sensors are of different types.

4. The system of claim 1 wherein;

at least one of said sensors is a motion sensor requiring an oscillator signal;

said control unit provides the oscillator signal; and

said multi-conductor cable includes a pair of conductors for providing DC power to said intrusion sensors and said interface circuits, a conductor for providing said oscillator signal to said at least one motion sensor, and a conductor for conveying mode control signals from said control unit to said sensors and for conveying alarm signals from said sensors to said control unit.

5. The system of claim 1 wherein said interface circuit includes:

a latch circuit;

comparator means operative in response to said mode control signals to provide respective output signals to said latch circuit;

circuit means operative in response to an alarm signal above a predetermined reference level to provide an input signal to said latch circuit and to provide an alarm indication on said cable;

a driver circuit operative in response to output signals from said latch circuit for energizing a sensor indicator in accordance with the mode associated with the selected mode control signal.

6. For use in an intrusion detection system in which a plurality of intrusion sensors are coupled via a system cable to a central control unit, an interface module coupling each sensor to said cable and comprising:

first means operative in response to mode control signals on one line of said cable from said central control unit for providing selected control signals for energizing sensor indicators associated with the intrusion sensors in accordance with the selected mode;

said mode control signals being respective signal levels corresponding to selected display modes of the sensor indicators denoting present and past occurrence of alarm signals produced by the associated sensors; and

means operative in response to intrusion detection by said sensors to provide an alarm signal on the same line of said cable for communication to said central control unit to cause an alarm indication at said central control unit irrespective of the selected display mode of the sensor indicators specified by the mode control signals.

7. The interface module of claim 6 wherein said first means includes first and second comparators, each having a respective reference source and operative in response to said mode control signals for providing outputs in accordance with the signal level of the mode control signals in relation to the reference signals;

latch means operative in response to the outputs from said first and second comparators for providing said selected control signals;

a bipolar detector operative in response to a differential intrusion detection signal to provide an output signal; and

a third comparator operative in response to said output signal from said bipolar detector to provide an alarm signal to said latch means when said output signal differs from an applied reference signal for said third comparator by a predetermined amount.

8. The interface module of claim 6 wherein said mode control signals are at respective signal levels corresponding to a reset mode in which a sensor indicator denotes the presence of an associated alarm signal as it occurs, a latch mode in which a sensor indicator remains on after an associated alarm signal has ceased, and a freeze mode in which a sensor indicator remains in the state it was in at the time this freeze mode is initiated.

9. For use in an intrusion detection system in which a plurality of intrusion sensors are coupled via a system cable to a central control unit, an interface module coupling each sensor to said cable and comprising:

first means operative in response to mode control signals on one line of said cable from said central control unit for providing selected control signals for energizing sensor indicators associated with the intrusion sensors in accordance with the selected mode;

said mode control signals being at respective signal levels corresponding to selected display modes of the sensor indicators denoting present and past occurrence of alarm signals produced by the associated sensors; and

means operative in response to intrusion detection by said sensors to provide an alarm signal on the same line of said cable for communication to said central control unit to cause an alarm indication at said central control unit irrespective of the selected display mode of the sensor indicators specified by the mode control signals;

said first means including comparator means operative in response to said mode control signals for providing outputs in accordance with the signal level of the mode control signals;

latch means operative in response to the outputs from said comparator means for providing said selected control signals;

a detector operative in response to an intrusion detection signal to provide an output signal; and

second comparator means operative in response to said output signal from said detector to provide an alarm signal to said latch means and said means operative in response to intrusion detection when said output signal differs from a reference signal for said second comparator means by a predetermined amount.