Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1999-09-29
2000-10-17
Pope, Daryl
Communications: electrical
Condition responsive indicating system
With particular system function
340511, 340533, 34031001, 34031005, G08B 2900
Patent
active
061338281
ABSTRACT:
A fire detection and alarm system has fire detecting devices of different types (T1,T2) and alarm means connected across supply lines. Both types of device normally apply a high impedance across the supply lines in a standby condition, and a low impedance in an alarm condition. The fire detecting devices are operable by a first voltage. This is lower than a second voltage applied, by a CCU, to the lines in an alarm condition for operating the alarm means. The alarm means respond to operating current supplied under different conditions to give respectively different kinds of fire warnings. Each first and second type of fire detecting device has current limiting means for differently limiting the respective current drain on the supply lines in the alarm condition. The CCU is operable to cause the supply line voltage to be momentarily reduced below the second voltage, so that the alarm means is momentarily deactivated, whereby the CCU can then respond to the supply line voltage, due to the respective current drain of the current limiting means, so as to apply the operating current to the alarm means to give the required fire warning. This enables priority to be given to a manual call point.
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
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