Multiple alarm condition detection and signalling

• US 4,385,287 A
• Filed: 12/02/1980
• Issued: 05/24/1983
• Est. Priority Date: 12/07/1979
• Status: Expired due to Term

• Current Assignee: RCA Security Systems Limited
• Original Assignee: Securicor Granley Systems Limited
• Inventors: Eatwell, Edgar G.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Crosland, Donnie Lee
• Application Number:
  US06/212,167
• Time in Patent Office: 903 Days
• Field of Search: 340/537, 340/521, 340/506-513, 340/531, 340/536, 340/538, 340/505, 340/660-664, 340/164 R, 340/310 R, 340/825.06, 340/825.07, 340/825.08 , 340/825.09, 340/825.1, 340/825.36, 340/825.37, 340/825.39, 340/825.42, 340/825.43, 340/825.54, 340/825.63, 340/825.64
• US Class Current: 340/537
• CPC Class Codes: G08B 19/00 Alarms responsive to two or more different undesired or abnormal conditions, e.g. burglary and fire, abnormal temperature and abnormal rate of flow
• CPC Class Codes: G08B 29/06 Monitoring of the line circuits, e.g. signalling of line faults

Abstract

A security system has a locality station sensing security risks such as fires, electrical faults and break-ins, being powered by a single line from a central station. The loading on the power supply is determined by logic circuits to give direct remote indications of the security state at the locality station. The power supply is a square wave which is altered in waveform to give alternative commands to the locality station, e.g. to sound a warning or to operate a fire sprinkler, while continuing to supply power. To enable maximum use of the single line and single square wave, the latter is treated as two separate signals in that loading by the locality station is selective as regards the polarities. Similarly the alternative commands available are doubled by using separate control of the durations of the positive and negative square wave portions, while continuing to supply power.

Claims

1. In a security system including a station at a locality to be secured, a control station for registering security sensing information communicated thereto by the locality station and for communicating command signals to the locality station, and a transmission cable for the communications in both directions between the control station and the locality station, equipment at the locality station comprising:

means to receive an ac signal from the transmission cable, the ac signal having a waveform comprising first and second portions, the first portions being generally towards one polarity in the ac signal and the second portions being generally towards the opposite polarity in the ac signal, alarm commands being communicated from the control station to the locality station as variations in the durations of the first and second portions of the ac signal;

first and second independently operable sensing means to provide respective outputs designative of security states;

first non-linear means to provide a loading only to said first portions of the waveform of the ac signal which loading is dependent selectively on the output of the first sensing means;

second non-linear means to provide a loading only to the second portions of the waveform of the ac signal, which loading is dependent selectively on the output of the second sensing means; and

means arranged to receive the ac signal and to respond to variations in the durations of said first and said second portions of said ac waveform to identify the alarm commands.

2. Equipment according to claim 1 wherein at least one of the first and second nonlinear means includes a first circuit connected to the cable, the first circuit comprising:

a normally closed contact, the opening of which is denotive of an alarm state,

a nonlinear device in shunt with the normally closed contact, and

a cable termination voltage reference device in series with the cable and the circuit.

3. Equipment according to claim 2 wherein:

the contact is installed at a position at the locality so as to be automatically actuated by an intruder.

4. Equipment according to claim 1 wherein at least one of the first and second nonlinear means includes a second circuit which comprises:

a normally open contact, the closing of which is denotive of an alarm state, and

a voltage reference device in series with said normally open contact, wherein

said second circuit is in shunt across the cable.

5. Equipment according to claim 4 wherein:

the contact is automatically actuable by an intruder at the locality.

6. Equipment according to claim 1 comprising:

further alarm sensing equipment, and an auxiliary power supply arranged to power the further alarm sensing equipment, wherein

said auxiliary power supply is in shunt across the cable, for being energized by said ac signal.

7. Equipment according to claim 1 comprising:

first and second equal value voltage reference devices connected opposingly across the cable as a cable termination at the location;

said equal value exceeding the values of any other voltage references devices shunting the cable at the locality equipment.

8. Equipment according to claim 1 comprising:

alarm command responsive means connected across the cable input to the location equipment, this means including,

a monostable having an input coupled to the cable and an output;

a data register having a clock input coupled to the cable, a data input coupled to the output of the monostable, and an output; and

an alarm command manifesting device coupled to the data register output.

9. A security system control station equipment, comprising:

means to apply an ac signal to a transmission point for communication of the ac signal to a locality equipment, the waveform of the ac signal comprising first and second portions of respective durations;

first and second duration controlling means arranged to respond to individual loadings offered by the locality equipment, in response to respective security conditions, respectively to the first portion and to the second portion of the waveform of the ac signal;

wherein

said duration controlling means is adapted to affect the durations of respectively the first and the second portions of the ac signals, thus impressing command signals thereon for their communication over a cable to the locality equipment from the transmission point.

10. Equipment according to claim 9 wherein the duration controlling means comprises:

a square wave oscillator having alternative durations of the positive polarity wave portions and having alternative durations of the negative polarity wave portions, wherein

selection inputs of the oscillator are arranged so as independently to select the alternative wave portion durations at the two polarities.

11. Equipment according to claim 10 having means to generate said selection inputs, comprising:

a series resistance at the connection to said cable

a logic circuit coupled to receive the voltage developed by said series resistance;

a set of voltage comparators and voltage references in the logic circuit coupled to give output digits depending on said developed voltage;

means in the logic circuit to route the output digits to serve as said selection inputs for appropriate control of said duration controlling means.

12. A security system comprising a control station equipment according to claim 11, said cable extending to a locality station, and equipment at the locality station comprising:

a set of on-off contacts associated with non-linear means and voltage reference devices whereby the conditions of said contacts give rise to a plurality of possible voltages at each of two polarities developed across said series resistance at the control station equipment; and

alarm command responsive means capable of distinguishing between plural possible durations at each polarity in the incoming ac wave from the control station, as distinct alarm commands.

13. A security system according to claim 12, wherein said alarm command responsive means comprises:

a monstable having an input coupled to the cable and an output;

a data register having a clock input coupled to the cable, a data input coupled to the output of the monostable and an output; and

an alarm command manifesting device coupled to the register output.

14. A security system according to claim 10 wherein the square wave oscillator comprises:

a first plurality of triggered monostables with different relaxation times and with their inputs connected in parallel;

a first selection circuit having separate data inputs coupled to individual outputs of the monostables, a control input and a single output; and

a second plurality of triggered monostables with different relaxation times and with their inputs connected in parallel to the single output of the first selection circuit;

a second selection circuit having separate inputs coupled to individual outputs of the monostables of said second plurality a control input, and a single output coupled to the commoned inputs of all the monostables of the first plurality;

the first and second selective circuits being each adapted to connect a selected one of its separate inputs to its single output, and the input selected depending on a control signal applied to its control input;

the control inputs thus serving as said selection inputs of said square wave oscillator; and

the square waves being supplied by alternate triggering of a selected monostable from either one of the plurality on the relaxation of a selected monostable from the other plurality.

15. A security system including equipment at a station to be secured, a control station having equipment for registering security sensing information communicated thereto by the locality station and for communicating command signals to the locality station, a transmission cable for the communications in both directions between the control station and the locality station, and means to apply an ac signal to the transmission cable, the equipment at the locality station comprising:

means to receive the signal from the transmission cable, the ac signal having a waveform comprising first and second portions, the first portions being generally towards one polarity in the ac signal and the second portions being generally towards the opposite polarity in the ac signal, alarm commands being communicated from the control station to the locality station as variations in the durations of the first and second portions of the ac signal;

first and second independently operable sensing means to provide respective outputs designative of security states;

first non-linear means to provide a loading only to said first portions of the waveform of the ac signal which loading means is dependent selectively on the output of the first sensing means; and

second non-linear means to provide a loading only to the second portions of the waveform of the ac signal, which loading is dependent selectively on the output of the second sensing means; and

means arranged to receive the ac signal and to respond to different alarm commands communicated to the location equipment by variations in the durations of, respectively, said first and said second portions of said ac waveform to identify the alarm commands;

and the equipment at the control station comprising means for varying the duration of the first or second portions responsive to the loading to the first or second portions of the ac waveform.

16. A security system comprising control station equipment, a cable and locality station equipment interconnected to the control station equipment by the cable, wherein the control signal equipment comprises:

means to apply an ac signal to the cable for communication of the ac signal to the locality station equipment, the waveform of the ac signal comprising first and second portions of respective durations, and first and second duration control means arranged to respond to individual loadings offered by the locality station equipment, in response to respective security conditions, respectively to the first portions and to the second portions of the waveform of the ac signal, the duration control means being adapted to affect the durations of respectively the first and the second portions of the ac signals, thus impressing command signals thereon for their communication over the cable to the locality station equipment from the control station equipment;

and wherein the locality station equipment comprises alarm command responsive means capable of distinguishing between a plurality of possible durations at each polarity in the incoming ac waveform from the control station equipment as distinct alarm commands, said alarm command responsive means comprising a monostable having an input coupled to the cable and an output, a data register having a clock input coupled to the cable, a data input coupled to the output of the monostable and an output and an alarm command manifesting device coupled to the register output.

17. A security system comprising control station equipment, a cable and locality station equipment interconnected to the control station equipment by the cable, wherein the control signal equipment comprises:

means to apply an ac signal to the cable for communication of the ac signal to the locality station equipment, the waveform of the ac signal comprising first and second portions of respective durations, and first and second duration control means arranged to respond to individual loadings offered by the locality station equipment, in response to respective security conditions, respectively to the first portions and to the second portions of the waveform of the ac signal, the duration control means being adapted to affect the durations of respectively the first and the second portions of the ac signals, thus impressing command signals thereon for their communication over the cable to the locality station equipment from the control station equipment;

wherein the locality station equipment comprises alarm command responsive means capable of distinguishing between a plurality of possible durations at each polarity in the incoming ac waveform from the control station equipment as distinct alarm commands, and

wherein the duration controlling means comprises a square wave oscillator having alternative durations of the positive polarity wave portions and having alternative durations of the negative polarity wave portions, selection inputs arranged so as independently to select the alternative wave portion durations at the two polarities, a first plurality of triggered monostables with different relaxation times and with their inputs connected in parallel, a first selection circuit having separate data inputs coupled to individual outputs of the monostables, a control input and a single output, and a second plurality of triggered monostables with different relaxation times and with their inputs connected in parallel to the single output of the first selection circuit, a second selection circuit having separate inputs coupled to individual outputs of the monostables of said second plurality, a control input, and a single output coupled to the commoned inputs of all the monostables of the first plurality, the first and second selective circuits being each adapted to connect a selected one of its separate inputs to its single output, and the input selected depending on a control signal applied to its control input, the control inputs thus serving as said selection inputs of said square wave oscillator, and the square waves being supplied by alternate triggering of a selected monostable from either one of the plurality on the relaxation of a selected monostable from the other plurality.

18. In a security system including a station at a locality to be secured, a control station for registering security sensing information communicated thereto by the locality station and for communicating command signals to the locality station, and a transmission cable for the communications in both directions between the control station and the locality station equipment at the locality station arranged so as in use to be energized by an ac power supply signal applied to the cable by the control station, means to receive the ac signal from the transmission cable the ac signal having a waveform comprising first and second portions, the first portions being generally towards one polarity in the ac signal and the second portions being generally towards the opposite polarity in the ac signal, alarm commands being communicated from the control station to the locality station as variations in the durations of the first and second portions of the ac signal, the locality station equipment comprising:

first and second sensing means to provide respective outputs designative of security station;

first non-linear means to provide a loading only to said first portions of the waveform of the ac signal which loading means is dependent selectively on the output of the first sensing means;

second non-linear means to provide a loading only to the second portions of the waveform of the ac signal, which loading is dependent selectively on the output of the second sensing means; and

means arranged to receive the ac signal and to respond to variations in the durations of said first or said second portions of said ac waveform to identify the alarm commands.

19. A security system control station equipment, comprising:

means to apply an ac power supply waveform to a transmission point for communication of the ac signal to a locality equipment arranged to be energized by the ac power supply waveform, the ac power supply waveform comprising first and second portions of respective durations;

first and second duration controlling means arranged to respond to individual loadings offered by the locality station equipment, in response to respective security conditions, respectively to the first portion and to the second portion of the ac power supply waveform wherein

said duration controlling means is adapted to affect the durations of respectively the first and the second portions of the ac power supply waveform, thus impressing command signals thereon for their communication over a cable to the locality equipment from the transmission point.