ALARM-MONITORING SYSTEM

• US 3,611,361 A
• Filed: 11/03/1969
• Issued: 10/05/1971
• Est. Priority Date: 11/03/1969
• Status: Expired due to Term

• Current Assignee: Mosler Incorporated (Diebold Nixdorf, Incorporated)
• Original Assignee: Donald E. Hansen, James A. Marquis, John H. Gallichotte, William J. Shaughnessy
• Inventors: Shaughnessy, William J., Gallichotte, John H., Hansen, Donald E., Marquis, James A.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Mooney, Robert J.
• Application Number:
  US04/873,387
• Time in Patent Office: 701 Days
• Field of Search: 340/213,408,150,151,206 179/1.5 343/6.5
• US Class Current: 340/505
• CPC Class Codes: G08B 26/002 only replying the state of the sensor

Abstract

A system for monitoring at a central station the condition, alarm or nonalarm, of a plurality of alarm condition sensors located at a remote station, including interrogation signal means at the central station for interrogating the remote station prior to transmission of each signal of a multisignal train, the interrogation occurring following the expiration of the randomlength delays initiated when signals are received from the remote station, thereby rendering the interrogation process and the resultant signal transmission process aperiodic in nature; a first transmitting means at said remote station responsive to the receipt of interrogation signals for transmitting a first widthmodulated binary signal train when none of the alarm condition sensors is in an alarm condition and a complete inversion thereof when an alarm condition sensor is in an alarm condition; a second transmitting means at the remote station also responsive to the interrogation signals for transmitting a second width-modulated binary signal train when none of the sensors is in an alarm condition, the second width-modulated train having as many signals as there are sensors individually monitored with each sensor associated with a different signal, and for transmitting an inversion of a sensor-associated signal when the associated sensor is in an alarm condition; detecting means at the central station for analyzing the output of the first transmitting means to determine if the first signal train, or a complete inversion thereof, was transmitted and to determine if a sensor-associated signal, or the inversion thereof, was transmitted; and a plurality of alarm indicators each corresponding to a different one of the remote station sensors being individually monitored, each indicator being activated when its respective remote station sensor is in an alarm condition and both an inversion of its respective sensor-associated signal and a complete inversion of the first signal train are detected.

Claims

1. A system for individually monitoring at a central station the condition, alarm or nonalarm, of a plurality of alarm condition sensors located at a remote station, said system comprising:

first transmitting means at said remote station which are responsive to each of said alarm condition sensors for transmitting to said central station a first sequence of widthmodulated binary signals when none of said alarm condition sensors is in an alarm condition and for transmitting to said central station a complete inversion of said first sequence of width-modulated binary signals when one of said sensors is in an alarm condition, second transmitting means at said remote station which are responsive to each of said sensors for transmitting to said central station a second sequence of width-modulated binary signals when none of said sensors is in an alarm condition, said second signal sequence having at least as many signals as there are sensors to be individually monitored with each sensor associated with a different signal, said second transmitting means operative to transmit an inversion of a sensor-associated signal when said associated sensor is in an alarm condition, means at said central station for interrogating said first and second remote station transmitting means prior to the transmission of each width-modulated signal or inversion thereof of said first and second sequences, first detecting means at said central station for analyzing the signals transmitted by said first transmitting means to determine if said complete inversion of first signal sequence thereof was transmitted, second detecting means at said central station for analyzing the signals transmitted by said second transmitting means to determine if said inversion of a sensor-associated signal was transmitted, and a plurality of alarm indicators each corresponding to a different one of said remote station sensors, and each responsive to both said first and second detectors, each said indicator being activated to alert central station personnel that its respective remote station sensor is in an alarm condition in response to both the detection by said first detecting means of the transmission of a complete inversion of said first signal sequence and the detection by said second detecting means of the transmission of an inversion of its respective sensor-associated signal.

2. The system of claim 1 further including a third detecting means for analyzing the signals transmitted by said first transmitting means to determine if at least one but less than all of said first signals are inverted, and a circuit fault indicator responsive to said third detecting means for altering central station personnel to the existence of a fault condition when at least one but less than all of said first signals are inverted.

3. The system of claim 1 further including fault-detecting means for determining when only one of said inverted first signal sequence and inverted sensor-associated signal is transmitted.

4. The system of claim 3 wherein said fault-detecting means includes Exclusive-OR circuit means responsive to both said first and second detecting means, for providing an output when only one of said first and second detecting means detects its respective signal condition.

5. The system of claim 1 wherein said first detecting means includes means to internally generate at said central station said first signal sequence, means responsive to said internally generated first signal sequence and the signals transmitted by said first transmitting means for providing a first output when at least one of said internally generated signals and said signals transmitted by said first transmitting means does not match and a second output when none of said internally generated signals and said signals transmitted by said first transmitting means match, and coincidence circuit means responsive to said first and second outputs for detecting when both outputs are present and thereby determining the existence of a complete inversion of said first signal sequence.

6. A system for monitoring at a central station the condition, alarm or nonalarm, of an alarm condition sensor located at a remote station, said system comprising:

a code generator at said remote station for generating a normal sequence of width-modulated binary signals, when said alarm condition sensor is in said nonalarm condition, and for generating an alarm sequence of width-modulated binary signals when said sensor is in said alarm condition, interrogation means at said central station for transmitting interrogation signals to said remote station, said interrogation signals being transmitted at least at the rate of one interrogation signal per width-modulated binary signal transmitted by said remote station, transmitting means at said remote station responsive to said interrogation signals for causing said code generator to transmit width-modulated signals of either said alarm or nonalarm sequence, each of said signals of said transmitted sequence being transmitted in response to receipt of a separate interrogation signal, and detector means at said central station for analyzing said transmitted signal sequence to determine the existence of an alarm condition at said remote station.

7. A system for monitoring at a central station the condition, alarm or nonalarm, of an alarm condition sensor located at a remote station, said system comprising:

a telephone line transmission means interconnecting said remote and central stations, said transmission means having a predetermined maximum transmission rate requiring a specified minimum lapsed time interval between the transmission of successive signals, interrogation signal initiation means at said central station for initiating interrogation signals, interrogation signal termination means at said remote station responsive to the receipt of an interrogation signal initiated by said central station for terminating said interrogation signal after a delay following receipt thereof at least equal to said minimum interval, code transmission means at said remote station for transmitting, in response to successive interrogation signals, a sequence of successive width-modulated binary signals at the rate of one binary signal per interrogation signal, said code transmission means including a multistage binary counter having an input responsive to the receipt of an interrogation signal for incrementing said counter and having a plurality of outputs from said stages connectable for facilitating transmission of a first repetitive sequence of width-modulated binary signal sequences, said counter stage outputs being connectable in different manners to produce different repetitive signal sequences, said counter in response to the receipt of an interrogation signal following transmission of the last binary signal of said sequence being reset and not responsive for transmitting a binary signal until receipt of the next interrogation signal, a detector means aT said central station for analyzing said transmitted signal sequence to determine the existence of an alarm condition at said remote station, said detector means including a multistage binary counter having an input responsive to the transmission of an interrogation signal for incrementing said counter and a plurality of counter stage outputs for facilitating generation of a second repetitive sequence of signals related to said first sequence, said counter stage outputs being connectable in different manners to produce different repetitive signal sequences related to said different repetitive signal sequences of said remote station counter, and counter synchronization means at said central station for resetting said central station counter in response to the failure of said remote station to transmit a width-modulated signal following receipt of an interrogation signal, thereby synchronizing said remote and central station counters.

8. The system of claim 7 wherein said remote station detector includes signal-sampling means operative in response to receipt of a binary signal for generating a sampling pulse for sampling said transmission line means to determine the nature of the binary signal transmitted, whereby the analysis of the received signals is independent of variations in transmission line delays.

9. The system of claim 1 wherein said first and second transmitting means collectively include a multistage binary counter having an input responsive to the receipt of an interrogation signal for incrementing said counter and having a plurality of counter stage outputs connectable for facilitating transmission of a first repetitive sequence of width-modulated binary signals, said outputs being connectable in different manners to produce different repetitive signal sequences, said counter in response to the receipt of an interrogation signal following transmission of the last binary signal of said sequence being reset and not responsive for transmitting a binary signal until receipt of the next interrogation signal, and wherein said detector means at said central station includes a multistage binary counter having an input responsive to the transmission of an interrogation signal for incrementing said counter and a plurality of counter stage outputs for facilitating generation of a second repetitive sequence of signals related to said first sequence, said counter stage outputs being connectable in different signal sequences related to said different signal sequences of said remote station counter, and wherein said central station further includes counter synchronization means for resetting said central station counter in response to the failure of said remote station to transmit a width-modulated signal following receipt of an interrogation signal, thereby synchronizing said remote and central station counters.

10. A system for monitoring at a central station the condition, alarm or nonalarm, of an alarm condition sensor located at a remote station, said system comprising:

a code generator at said remote station for generating a normal sequence of binary signals, when said alarm condition sensor is in said nonalarm condition, and for generating an alarm sequence of binary signals when said sensor is in said alarm condition, interrogation means at said central station for transmitting interrogation signals to said remote station, said interrogation signals being transmitted at least at the rate of one interrogation signal per binary signal transmitted by said remote station, transmitting means at said remote station responsive to said interrogation signals for causing said code generator to transmit signals of either said alarm or nonalarm sequence, each of said signals of said transmitted sequence being transmitted in response to receipt of a separate interrogation signal, randomizing means for randomly varying the time interval between successive binary signal transmissions, and detector means at said central station for analyzing said traNsmitted signal sequence to determine the existence of an alarm condition at said remote station.

11. The system of claim 10 wherein said central station interrogation means includes a delay circuit for initiating said interrogation signals following receipt of transmitted binary signals after delay intervals, and wherein said randomizing means includes means associated with said delay circuit for randomly varying said delay intervals and thereby randomly varying the time interval between successive binary signal transmissions.

12. The system of claim 10 wherein said code generator includes a multistage binary counter having an input responsive to the receipt of successive interrogation signals for successively incrementing said counter and having a plurality of outputs from said stages connectable for facilitating transmission of a first sequence of binary signals when successively incremented, said counter stages being connectable in different manners to produce different signal sequences, and wherein said detector means includes a multistage binary counter having an input responsive to the transmission of an interrogation signal for incrementing said counter and having a plurality of counter stage outputs for facilitating generation of a second sequence of signals related to said first sequence, said detector counter stages being connectable in different manners to produce different signal sequences related to said first signal sequences of said remote station, and signal-sequence-changing means activated at said central station for similarly altering the interconnection of said remote station counter outputs and the interconnection of said central station counter outputs to thereby similarly alter the binary signal composition of said remote and central station binary signal sequences.

13. The system of claim 1 further including randomizing means for randomly varying the time interval between successive binary signal transmissions.

14. The system of claim 13 wherein said central station interrogation means includes a delay circuit for initiating said interrogation signals following receipt of transmitted binary signals after delay intervals, and wherein said randomizing means includes means associated with said delay circuit for randomly varying said delay intervals and thereby randomly varying the time interval between successive binary signal transmissions.

15. A system for individually monitoring at a central station the condition, alarm or nonalarm, of a plurality of alarm condition sensors located at a remote station, said system comprising:

first transmitting means at said remote station which are responsive to each of said alarm condition sensors for transmitting to said central station a normal sequence of width-modulated binary signals when none of said alarm condition sensors is in an alarm condition and for transmitting to said central station an alarm sequence of width-modulated binary signals when one of said sensors is in an alarm condition, said transmitting means including multistage binary counting means having input means responsive to the receipt of successive interrogation signals for successively incrementing said counting means and having a plurality of outputs from said stages connectable for facilitating transmission of said sequences of signals when successively incremented, said stages being connectable in different manners to produce different signal sequences, second transmitting means at said remote station which are responsive to each of said sensors for transmitting to said central station a sensor identity sequence of width-modulated binary signals when none of said sensors is in an alarm condition, said sensor identity signal sequence having at least as many signals as there are sensors to be individually monitored with each sensor associated with a different signal, said second transmitting means operative to transmit an inversion of a sensor-associated signal when said associated sensor is in an alarm coNdition, means at said central station for interrogating said first and second remote station transmitting means prior to the transmission of each width-modulated signal, first detecting means at said central station for analyzing the signals transmitted by said first transmitting means to determine if said alarm signal sequence was transmitted, second detecting means at said central station for analyzing the signals transmitted by said second transmitting means to determine if said inversion of a sensor-associated signal was transmitted, said detecting means including multistage counting means having an input responsive to the transmission of an interrogation signal for incrementing said counter and having a plurality of counter stage outputs for generation of a signal sequence related to said normal signal sequence, and counter outputs being connectable in different manners to produce different signal sequences related to said different signal sequences of said remote station, a plurality of alarm indicators each corresponding to a different one of said remote station sensors, and each responsive to both said first and second detectors, each said indicator being activated to alert central station personnel that its respective remote station sensor is in an alarm condition in response to both the detection by said first detecting means of the transmission of said alarm signal sequence and the detection of said second detecting means of the transmission of an inversion of its respective sensor-associated signal, and signal-sequence-changing means activated at said central station for similarly altering the interconnection of said remote station counter outputs and the interconnection of said central station counter outputs to thereby similarly alter the binary signal composition of said remote and central station binary signal sequences.

16. The system of claim 10 wherein said transmitting and interrogating means include carrier frequency signal generators and wherein the output of said code generator frequency modulates the output of said transmitting carrier frequency signal oscillator.

17. The system of claim 1 further including a third detecting means for analyzing the signals transmitted by said first transmitting means to determine if at least one but less than all of said first signals are inverted, said third detecting means providing an output signal upon inversion of at least one but less than all of said first signals, a circuit fault indicator responsive to said output of said third detecting means for alerting central station personnel to the existence of a fault condition when said output of said third detecting means if produced for a specified interval indicating multiple inversions of at least one but less than all of said first signals.

18. The system of claim 6 further including means at said remote station for selectively enabling and disabling said sensor, a second code generator at said remote station for generating different sensor status signals indicating the enabled and disabled status of said sensor, said status signals being input to said transmitting means for transmission to said central station, sensor status detector means at said central station responsive to said transmitted status signals for indicating a change in status of said sensor, and means at said central station for transmitting to said remote station a signal indicating detection by said status detector of a change in status of said sensor, thereby alerting remote station personnel to the fact that central station personnel are aware of the changed status of said sensor. In a system having a fault detector and a fault indicator responsive to said detector for indicating the existence of a fault, a signalling circuit for signalling failure of said fault-responsive indicator, said signalling circuit comprising:

a transistor having its emitter-collector path in series with said fault indicator and its base responsive to said fault detector for allowing current from a source to flow through and activate said fault indicator in response to an output from said fault detector accompanying the detection of a fault, said transistor being biased to conduct insufficiently to activate said fault indicator in the absence of said fault detector output, resistive means connected to pass said current flow through said indicator, a signal device responsive to the voltage across said resistive means for activating said signal device when said voltage is zero, due to interruption of said base, failure of said source, or failure of said fault indicator, said signal device remaining unactivated in response to the existence of voltages across said resistive means due to said current flow and said insufficient transistor conduction.