Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1982-05-03
1985-06-11
Crosland, Donnie L.
Communications: electrical
Condition responsive indicating system
With particular system function
340506, 340508, 340510, 340511, G08B 2900
Patent
active
045231834
ABSTRACT:
A microcomputer controlled circuit arrangement for sensing fire and burglar alarms in the presence of undesired fault conditions, such as opens or shorts, on monitored communication lines. The arrangement includes transistor-resistor sensing circuitry which is shared by a plurality of monitored communication lines, each of which comprises a first pair of conductors connected to a first contact of an alarm sensor and a second pair of conductors connected to a second alarm sensor contact. The sensing circuitry is connected through a multiplexer to each one of the lines one at a time under control of the microcomputer to detect any fault thereon and any alarm provided by the sensor contacts. The sensing circuitry is responsive to impedance conditions on the four conductors furnishing a plurality of output voltages which are examined by comparators that, in turn, generate combinational logic voltages signifying the alarm-fault state of a monitored line.
REFERENCES:
patent: 4079363 (1978-03-01), Wilson, Jr.
patent: 4253091 (1981-02-01), Frydman
patent: 4283717 (1981-08-01), Caldwell et al.
patent: 4414539 (1983-11-01), Armer
patent: 4441100 (1984-04-01), Galloway
AT&T Bell Laboratories
Crosland Donnie L.
Davis Charles H.
Padden F. W.
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