Electrical transmission or interconnection systems – Switching systems – Condition responsive
Patent
1981-06-22
1983-06-07
Eisenzopf, Reinhard J.
Electrical transmission or interconnection systems
Switching systems
Condition responsive
361203, 361204, H01H 4700
Patent
active
043873065
ABSTRACT:
A vital contact checking circuit which senses the state of the back contact of a relay in either a dynamic or static situation. In the former, a signal is coupled from its source to a detector by a coupling device, such as a transformer, and an additional winding on the transformer is connected to the heel and back contact of the relay whose contact is being checked. When a circuit is established through the back contact the additional winding is short circuited, thereby preventing the signal from the source from reaching the detector and effectively eliminating it. A variation of this scheme, also for use in a dynamic situation, involves using the coil structure in a resonant circuit, the sensing winding causing detuning when the back contact is closed so that again, the detector does not receive the signal from the source. For performing a vital check on a static contact, another scheme is utilized because a failure in the oscillator or detector circuit of the schemes already described would give the same indication as a closed back contact. Therefore, the primary and secondary windings of the main transformer are wound on separate cores and the sensing winding links the individual cores so that the detector produces an output only if the sensed contact is indeed closed.
REFERENCES:
patent: 3383504 (1968-05-01), Dennison
patent: 3428868 (1969-02-01), Duckitt et al.
patent: 4225899 (1980-09-01), Sotiriou
patent: 4236149 (1980-11-01), Soyck
Eisenzopf Reinhard J.
General Signal Corporation
Kleinman Milton E.
Ohlandt John F.
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