Circuit for detecting abnormality in feeder

Details Circuit for detecting abnormality in feeder Circuit for detecting abnormality in feeder

1987-01-22

1988-05-31

Schreyer, Stafford D.

Telephonic communications

Diagnostic testing, malfunction indication, or electrical...

Testing of network terminating interface, subscriber trunk...

379 27, 324555SS, H04M 124, H04M 308

Patent

active

047486520

ABSTRACT:
A detecting circuit for detecting electric abnormality of a pair of feeders is provided with resistors R.sub.A and R.sub.B converting the abnormality of the feeders into a change in voltage, transistors (Q.sub.8, Q.sub.9 and Q.sub.10) supplying or interrupting a current I.sub.B in response to presence or absence of an abnormal state, transistors (Q.sub.5, Q.sub.6 and Q.sub.17) drawing in or blocking a current I.sub.A in response to the abnormal state, a current subtraction element (I) conducting a subtraction of the currents I.sub.B and I.sub.A on an absolute value basis, a current addition element (II) conducting an addition of the currents I.sub.A and I.sub.B, a current addition element (III) adding the output currents of the current subtraction element (I) and current addition element (II), and a voltage comparator (6) subjecting the output current of the current addition element (III) to current-voltage conversion and comparing a voltage thus obtained with a reference voltage so as to obtain an abnormality detection signal, which is used to interrupt the feeding of electricity to the paired feeders when an abnormality is detected.

REFERENCES:
patent: 4385336 (1983-05-01), Takeshita et al.
patent: 4424479 (1984-01-01), Brown

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