Abstract: A telephone line feed circuit is disclosed including a protective device which is located on the line ahead of the feeding device. The protective device reduces the voltage variations at the terminals of the feeding voltage in the event of overvoltage on the line. This advantageously protects the cross points of the switch against overvoltage.

Abstract: A circuit for protecting a telephone junctor from excessive alternating or direct current voltage includes a diode bridge connected to the junctor. A first threshold detector connected to the diode bridge detects excessive positive voltages and a second threshold detector connected to the diode bridge detects excessive negative voltages. The output of the two threshold detectors are applied to a temporization circuit which inhibits an over-voltage indication signal from being generated by transient over-voltages. The temporization circuit also sustains an over-voltage indication signal when the signal waveform of an alternating-current over-voltage passes through zero. A circuit responsive to an over-voltage indication signal inhibits application of power to the junctor circuit.