Communications: electrical – Systems – Call station
Patent
1975-07-02
1977-06-28
Curtis, Marshall M.
Communications: electrical
Systems
Call station
340412, G08B 2500
Patent
active
040329089
ABSTRACT:
A plurality of alarm conductors are coupled to a multiplexer which connects the conductors one at a time in sequence to the input of an alarm detector which detects alarm conditions on the conductors. A shift register having the same number of stages as the number of alarm conductors has its input coupled to the multiplexer output and its output coupled back to its input to form a recirculating serial memory. The shift register is clocked in synchronism with the multiplexer. The output of the shift register is selectively coupled through a switchable memory output control to the input of the alarm detector to recall a previous alarm condition on one or more of the alarm conductors. A second shift register having a number of stages equal to an integral multiple of the number of alarm conductors has its input coupled to the output of the alarm detector means. The second shift register is also clocked in synchronism with the multiplexer. An exclusive OR circuit has one input coupled to the output of the second shift register, another input coupled to the output of the alarm detector, and the output coupled to the control means for a data transmitter which transmits the alarm to a remote location. The second shift register and exclusive OR circuit limit the number of times the alarm is transmitted to the remote location.
REFERENCES:
patent: 3641266 (1972-02-01), Stults et al.
patent: 3792466 (1974-02-01), Arnold et al.
patent: 3812487 (1974-05-01), Burton
patent: 3900845 (1975-08-01), Tsuiki et al.
patent: 3921168 (1975-11-01), Dunbar
Horn Barry N.
Rice Richard C.
Automated Systems, Inc.
Curtis Marshall M.
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