Alarm system

Communications: electrical – Condition responsive indicating system – Specific condition

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Details

340527, 340652, G08B 1314, G08B 2300

Patent

active

049529129

ABSTRACT:
An alarm system comprises of a closed circuit includes an alarm cord connected to a DC power source, a disconnect signal detector having an inverter circuit and a thyristor and a push-button switch. An alarm generator produces an alarm sound by the detection signal from the disconnect signal detector. A first charging-discharging circuit is connected to the DC power source through a first transistor which is turned on when the push-button switch is depressed, and a first Schmitt trigger circuit transmits a connect signal to the disconnect signal detector only for a time period set by the first charging-discharging circuit. The Schmitt trigger circuit transmits a disconnect signal to the disconnect signal detector after the setting period determined by the first charging-discharging circuit. A second charging-discharging circuit is connected to the DC power source through a second transistor to be turned on when the push-button switch is depressed, and a second Schmitt trigger circuit transmits a signal to cause the alarm generator to produce the alarm sound to indicate the start of alarm cancellation only for a time period set by the second charging-discharging circuit. The first and the second charging-discharging circuits constituting the timers can be energized by the current flowing through the first and the second transistors, respectively. The period of time of the cancellation mode and the period of time producing the alarm cancellation start sound at the time of the cancellation are set by the first and the second charging-discharging circuits, respectively.

REFERENCES:
patent: 4028691 (1977-06-01), Zeder
patent: 4151506 (1979-04-01), Schoenmetz
patent: 4284983 (1981-08-01), Lent
patent: 4300130 (1981-11-01), Fotheringham
patent: 4658242 (1987-04-01), Zeder

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