Communications: electrical – Systems – Timer control
Patent
1974-11-12
1976-02-10
Caldwell, John W.
Communications: electrical
Systems
Timer control
324182, 340267R, G08B 100, G04F 1000
Patent
active
039381285
ABSTRACT:
A warning circuit particularly suited for indicating that an intermittently operated device has been operated for a predetermined cumulative length of time. The circuit utilizes a coulometer as a current integrator that accumulates the intermittent periods of time during which the device operates. At the end of the predetermined cumulative length of time, the impedance of the coulometer changes from a low level to a relative higher level. This change in impedance renders a first transistor conductive and results in a warning indication. A second transistor is latched into a state of conductivity that causes a feedback current to flow through the coulometer to maintain it in its high impedance condition. The warning indication is controlled by an amplifier circuit which, in turn, is controlled by the second transistor. Once the high impedance of the coulometer is achieved, the second transistor at all times retains its state of conductivity indicative of this condition, but the amplifier circuit is operative only when the intermittently operated device is in operation.
REFERENCES:
patent: 3546693 (1970-12-01), Bissett et al.
Pidsosny Richard A.
Zimmer John
Brown Robert W.
Caldwell John W.
Ford Motor Company
Myer Daniel
Zerschling Keith L.
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