Communications: electrical – Systems – Call station
Patent
1974-09-20
1976-02-10
Caldwell, John W.
Communications: electrical
Systems
Call station
340 59, G08B 2100
Patent
active
039381170
ABSTRACT:
A critical liquid-level warning circuit for association with a liquid-level indicating circuit, the indicating circuit including a sensing device that provides a voltage which varies between upper and lower voltage limits as a function of the level of a liquid. The warning circuit is particularly suitable for use in indicating a low fuel level in the fuel tank of a vehicle and, in the preferred embodiment, includes a first operational amplifier responsive to the sensing device voltage and a second operational amplifier that controls the actuation of a warning device. A delay circuit is interposed between the first and second operational amplifiers. The output of the first operational amplifier changes from one condition to another condition upon occurrence of a critical liquid level. The delay circuit provides a voltage which varies in magnitude as a function of time elapsed subsequent to the change in condition of the output of the first operational amplifier. This variable voltage controls the second operational amplifier. Preferably, the second operational amplifier circuit includes means for delaying the de-actuation of the warning device, thereby, to prevent intermittent warning device operation.
REFERENCES:
patent: 3333469 (1967-08-01), Godfrey
patent: 3534352 (1970-10-01), Gallagher
Brown Robert W.
Caldwell John W.
Ford Motor Company
Myer Daniel
Zerschling Keith L.
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