Automatically resetting protection arrangement for a telephone subscriber line interface circuit

Abstract From the Canadian patent

Abstract of the Disclosure, A protection arrangement for coupling a two-wire line to a SLIC includes surge protecting triacs between each wire and ground and normally closed contacts coupling the wires to the SLIC. The triacs are triggered via varistors coupled to the wires on the SLIC side of the contacts, which are opened in response to over-voltages on the line, as detected via a diode bridge and threshold circuit. The triacs are thereby not triggered during over-voltage conditions so that their power dissipation is reduced during such faults whereas, they respond rapidly to surge conditions which accordingly need not be handled by the contacts. - i -