Communications: electrical – Systems – Call station
Patent
1975-10-02
1977-07-19
Swann, III, Glen R.
Communications: electrical
Systems
Call station
1791751A, 340224, 340248E, 340409, G08B 2100
Patent
active
040372227
ABSTRACT:
The operability of one or more audio speakers is monitored by continuously transmitting a non-audio signal on the lines connecting to the speakers and providing a vibration sensitive transducer such as a piezoelectric transducer which continuously picks up the signal. The output from the transducer couples to detection circuitry which may comprise an amplifier and gate or trigger circuit. The output of the detection circuitry couples either via the existing speaker lines or via a separate supervision line to an alarm device. When the speaker or speaker lines are inoperative the non-audio signal is not present and the gate circuit transmits an alarm signal to an alarm device. In one embodiment the detection circuitry is supplied power directly from the speaker lines via a rectifier means. In another embodiment the detection circuitry includes an oscillator, one associated with each speaker and each constructed to oscillate at a different frequency. With this arrangement the supervisory line may connect to a decoder for sensing the oscillator frequency when a fault occurs to thereby identify the malfunctioning speaker.
REFERENCES:
patent: 1958153 (1934-05-01), Pearson et al.
patent: 2393021 (1946-01-01), Cheek
patent: 2525697 (1950-10-01), Lurie
patent: 3656158 (1972-04-01), Goodwater
patent: 3707708 (1972-12-01), Dan
Gulf & Western Manufacturing Company (Systems)
Swann III Glen R.
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