Alarm and reset circuit for a countdown timer

Details Alarm and reset circuit for a countdown timer Alarm and reset circuit for a countdown timer

1984-08-10

1985-07-23

Roskoski, Bernard

Horology: time measuring systems or devices

Time interval

Electrical or electromechanical

368250, 368254, G04F 800

Patent

active

045306079

ABSTRACT:
A battery-powered alarm and reset circuit for a conventional electromechanical countdown timing mechanism which drives a set of cam-actuated main contacts. The circuit renders both a visual and an audible alarm at zero countdown time. The rotation of a timer knob closes the main contacts which readies the digital NAND gate logic of the circuit to a state preliminary to oscillation. At zero countdown time, one of the NAND gates goes into oscillation to generate a sequence of relatively low-frequency pulses in response to the opening of the main contact at zero countdown time. The low-frequency pulses activate an LED light to render a visual blinking alarm and an electrical horn to render an audible beeping alarm. Both alarms continue indefinitely until momentary manual closure of a reset switch stops the NAND gate from oscillating.

REFERENCES:
patent: 2799847 (1957-07-01), Harris
patent: 3187319 (1965-06-01), Crawford

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