Transmission line-monitoring apparatus for use in a fire alarm system
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United States of America Patent
Stats
-
May 19, 1998
Grant Date -
N/A
app pub date -
Aug 8, 1995
filing date -
Aug 18, 1994
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A transmission line-monitoring apparatus which is able to detect the occurrence of a short circuit even when a line has a large resistance and also to speedily disconnect the short-circuited transmission line upon detection of a short circuit. When a short circuit occurs between branched transmission lines on the output side of the apparatus, a short-circuit detection circuit contained in the transmission-line monitoring apparatus detects this short circuit so as to send a short-circuit detection signal to a line-disconnecting control circuit. Then, the control circuit is operated so as to cause a constant current circuit to interrupt the supply of a base current to a transistor, thereby disconnecting a short-circuited output branched transmission line from a corresponding input branched transmission line.
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