Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1999-04-15
2000-03-21
Pope, Daryl
Communications: electrical
Condition responsive indicating system
With particular system function
340 51, 340538, 34031001, 34031005, G08B 2900
Patent
active
060407697
ABSTRACT:
A fire alarm system has detecting devices and alarm devices connected in parallel across the same supply lines. A control unit (CCU) supplies a first voltage to operate the detecting devices and a second higher voltage to operate the alarm devices. When a fire is detected, signalling means, in the detecting device, produce a change of state signal which causes impedance switching means to switch from a high to a low impedance state. This causes a current drain across the supply lines which is recognized by the CCU as the fire detection signal, which then applies the second voltage to the lines. Voltage responsive means respond to the second voltage to cause the impedance switching means to switch to the high line impedance state. The current drain is thereby reduced to conserve battery power. This avoids large current drains when several detecting devices respond to the fire (e.g. when smoke detectors are triggered by spreading smoke). The voltage responsive means may include threshold voltage means. Additional voltage responsive means cause the impedance switching means to switch to a high impedance state, whenever the line voltage falls below a predetermined level below the first voltage. Circuitry is also described for maintaining the current drain on the supply lines substantially constant, for latching an alarm state, for delaying operation of the impedance switching means to enable the voltage on the supply lines to be switched rapidly between different levels without causing the impedance switching means to be in its low impedance state, and for operating on different polarities.
REFERENCES:
patent: 4812821 (1989-03-01), Santy et al.
patent: 4949359 (1990-08-01), Voillat
patent: 5705979 (1998-01-01), Fierro et al.
Apollo Fire Detectors Limited
Gable R. Lewis
Pope Daryl
LandOfFree
Detecting device and an alarm system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Detecting device and an alarm system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detecting device and an alarm system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-733683