SECURITY SIGNALLING WITH ALARM IDENTIFICATION

• US 3,760,359 A
• Filed: 12/14/1971
• Issued: 09/18/1973
• Est. Priority Date: 12/14/1971
• Status: Expired due to Term

• Current Assignee: Albert N. Mcquown Jr
• Original Assignee: Albert N. Mcquown Jr
• Inventors: McQuown, Albert N. Jr.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Curtis, Marshall M.
• Application Number:
  US05/207,908
• Time in Patent Office: 644 Days
• Field of Search: 340/164R,416,280,216,276,310
• US Class Current: 340/534
• CPC Class Codes: G08B 25/018 Sensor coding by detecting magnitude of an electrical parameter, e.g. resistance

Abstract

A security system is provided which includes a central monitoring system interconnected by a two-wire telephone circuit to one or more protection loops, each being composed of one or more series-connected reporting devices or stations. A DC power supply is located in the control station for generating a supervisory current flow between the control station and the protection loop, and each reporting device is composed of a signal generator in parallel with a low resistance shunt arranged to be broken by the detected occurrence of an event sought to be observed. Detection of the event interrupts the shunt to route the supervisory current through its associated signal generator, thereby developing a voltage greater than a predetermined value. The associated signal generator is then activated by the flow of supervisory power, whereby a signal current of preselected character is superimposed on the supervisory current. The control station registers the occurrence of the event by noting the presence of the superimposed signal current, and identifies the particular detector circuit by identifying the preselected characteristic of the signal being generated. Additionally, the routing of the supervisory current through the signal generator may be made to cause a significant decrease in the magnitude of this current. Concurrent registration of the occurrence of an event or the indication of a line fault may be noted at the control station by sensing the magnitude of the supervisory current and responding to a change of predetermined amount.

Claims

1. An electrical security system or the like, comprising a source of power, transmission means interconnected with said source of power for conducting a current flow, a normally closed detecting circuit interconnected with said transmission means having an impedance selected to maintain a voltage lower than a predetermined threshold value and openable upon the occurrence of a preselected event, and an identification circuit means connected in parallel with said detecting circuit and including means responsive to an increase in said voltage above said threshold value for superposing on said current flow an information signal representative of said preselected event.

2. The signal generator described in claim 1, further including modulating means for superimposing said signal on said current flow in said transmission means upon the occurrence of said predetermined event.

3. The signal generator described in claim 2, further including latching means for maintaining activation of said signal generator upon subsequent reclosure of said detecting circuit.

4. The system described in claim 3, further including first sensing means for deriving a first indication in response to the occurrence of said superimposed signal in said transmission sysTem.

5. The system described in claim 4, further including amplifying means for deriving a signal voltage functionally corresponding to said superimposed signal current in said transmission means.

6. The system described in claim 5, further including a signal determining means responsive to an information signal having characteristics substantially corresponding to the characteristics of said superimposed signal current, and a switching means for selectively coupling said amplifying means to said signal determining means, and an indicating means responsive to said signal determining means for announcing the occurrence of said event.

7. A security system or the like having a central monitoring station and at least one remote station, comprising a source of DC power for generating a supervisory DC current of preselected magnitude, a transmission means for carrying said DC current between said stations, a first conductive path of relatively low resistance at said remote station and connected to said transmission means for conducting substantially all of said DC current flowing between said stations at said preselected magnitude, a second path also connected to said transmission means including a signal generating means for producing a periodic signal having a preselected frequency characteristic upon interruption of said first path and routing of said DC current through said second path, and means for superimposing said periodic signal on said supervisory DC current flowing in said transmission means.

8. The system described in claim 7 further including a detecting means responsive to the occurrence of a preselected event for interrupting at least momentarily said first conductive path.

9. The system described in claim 16 wherein said second path further includes a sensing means for determining the occurrence of an interruption in said DC current flow in said first conductive path, and a current interrupting means responsive to said sensing means to maintain said interruption of DC current from said first path.

10. The system described in claim 9, further including at said central monitoring station a first modulated current sensing means for deriving a first indication in response to the occurrence of said superimposed periodic signal, and an AC coupling means and amplifying means for deriving an AC voltage functionally corresponding to said superimposed periodic signal.

11. The system described in claim 18, further including resonating means responsive to only an AC input voltage having frequency characteristics substantially corresponding to the frequency characteristics of said superimposed periodic signal, switching means for selectively coupling said amplifying means to said resonating means in response to said first indication, and signal detection means responsive to said resonating means for indicating the identity of said event.

12. The system described in claim 19, further including a DC current sensing means for deriving a second indication in response to a change in magnitude of said supervisory DC current to less than a preselected magnitude.

13. The system described in claim 20, wherein said signal generating means includes delay means responsive to the initial flow of current in said second path for decreasing said supervisory DC current during a discrete time interval initiated by the occurrence of said event.

14. The system described in claim 10, further including voltage generating means responsive to said superimposed signal in said transmission system for generating a voltage increment of preselected magnitude, a variable frequency oscillator for generating a tone frequency related to the magnitude of said voltage increment, and alarm means for providing an audible tone corresponding in pitch to said tone frequency, said oscillator also adapted to receive at least one additional voltagE increment of said preselected magnitude and to generate said tone frequency as a function of the sum of said increment from said voltage generating means and said additional increment.

15. A security system or the like having a central monitoring station and at least one remote station, comprising a source of DC power for generating a supervisory DC current of preselected magnitude, a transmission means for carrying said DC current between said stations, a first conductive path of relatively low resistance at said remote station and connected to said transmission means for conducting substantially all of said DC current flowing between said stations at said preselected magnitude, a second path also connected to said transmission means including a signal generating means for producing a code signal having a preselected time-dependent characteristic upon interruption of said first path and routing of said DC current through said second path, and means for superimposing said code signal on said supervisory DC current flowing in said transmission means.

16. The system described in claim 15 further including a detecting means responsive to the occurrence of a preselected event for interrupting at least momentarily said first conductive path.

17. The system described in claim 16 wherein said second path further includes a sensing means for determining the occurrence of an interruption in said DC current flow in said first conductive path, and a current interrupting means responsive to said sensing means to maintain said interruption of DC current from said first path.

18. The system described in claim 17, further including at said central monitoring station a first modulated current sensing means for deriving a first indication in response to the occurrence of said superimposed code signal, and an AC coupling means and amplifying means for deriving a code voltage functionally corresponding to said superimposed code signal.

19. The system described in claim 18, further including decoding means responsive to only an input code voltage having time characteristics substantially corresponding to the time characteristics of said superimposed code signal, switching means for selectively coupling said amplifying means to said decoding means in response to said first indication, and signal display means responsive to said decoding means for indicating the identity of said event.

20. The system described in claim 19, further including a DC current sensing means for deriving a second indication in response to a change in magnitude of said supervisory DC current to less than a preselected magnitude.

21. The system described in claim 20, further including a delay means as part of said signal generator responsive to the initial flow of current in said second path for decreasing said DC current for a discrete preselected time interval following the occurrence of said event.

22. The system described in claim 21, further including voltage generating means responsive to said superimposed signal in said transmission system for generating a voltage increment of preselected magnitude, a variable frequency oscillator for generating a tone frequency related to the magnitude of said voltage increment, and alarm means for providing an audible tone corresponding in pitch to said tone frequency, said oscillator also adapted to receive at least one additional voltage increment of said preselected magnitude and to generate said tone frequency as a function of the sum of said increment from said voltage generating means and said additional increment.