Fail-safe acknowledging circuit

Details Fail-safe acknowledging circuit Fail-safe acknowledging circuit

1980-05-27

1982-02-02

Robinson, Thomas A.

Communications: electrical

Condition responsive indicating system

With particular system function

340 47, 340 52D, 340507, 180170, 180171, 364426, 246 5, 246182R, 246187R, B61L 1500, B61L 300, G08B 2300

Patent

active

043142370

ABSTRACT:
A fail-safe acknowledging circuit having a plurality of relay switching contacts having a predetermined order of more restrictive significance. A differentiating circuit selectively interconnected by certain ones of the plurality of relay switching contacts for establishing a selected one of a plurality of charging potential levels from a d.c. voltage source. A latching circuit is conditioned by a holding voltage and is set by momentarily closure of an acknowledging switch to produce a.c. signals which are fed to one input of a two-input AND gate. A checking circuit monitors the voltage level of the d.c. voltage source and verifies the integrity of the differentiating circuit to produce a d.c. potential which is conveyed to the other input of the two-input AND gate. The output of the two-input AND gate supplied to a time delay circuit for normally energizing a brake release relay and for deenergizing the brake release relay if the acknowledging switch is not momentarily reclosed within a given period of time after the reception of a more restrictive speed command signal.

REFERENCES:
patent: 3696356 (1972-10-01), Franke et al.
patent: 4177459 (1979-12-01), Darrow

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