Communications: electrical – Audible indication – Pneumatic-type sound producer
Patent
1974-04-24
1976-02-17
Pitts, Harold I.
Communications: electrical
Audible indication
Pneumatic-type sound producer
340409, G08B 2500, G08B 2600
Patent
active
039394603
ABSTRACT:
Fire alarm and intrusion alarm conductors are wired from a plurality of dwellings to a nearby data transmitter circuit which is linked by a single pair of conductors to a remote data receiver circuit. The alarm conductors are sequentially scanned in the data transmitter circuit by a binary counter which sequentially enables or opens gates that are coupled to the alarm conductors. When an alarm condition is detected on one of the alarm conductors, the scanning counter is stopped and the counter number is converted from parallel form to serial form. The serial number is transmitted from the data transmitter circuit to the data receiver circuit. The least significant bit of the number signifies whether the alarm is a fire or an intrusion. The remaining bits signify the location. In the receiver circuit, the received data is converted back to parallel form and is printed out on a printer. The transmitted data includes a first bit which is always a binary 1 and a last bit which is always a binary zero. The first bit starts the serial to parallel converter in the receiver circuit and the last bit insures that the output of the parallel to serial converter in the transmitter circuit is left in the low state after the transmission is completed. The data is preferably transmitted from the transmitter circuit to the receiver circuit by frequency shift keying. The data is clocked out of the parallel to serial converter and into the serial to parallel converter by clock pulses which are derived by dividing down the frequency of the frequency shift keying carrier.
REFERENCES:
patent: 3435416 (1969-03-01), Kretsch
patent: 3697984 (1972-10-01), Atkinson
patent: 3735396 (1973-05-01), Cetchell
patent: 3765016 (1973-10-01), Bert
Horn Barry N.
Rice Richard C.
Swain Richard S.
Fuller Henry C.
Horn Barry N.
Pitts Harold I.
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