Patent ID: RE39406

Claim:
A telephone line coupler circuit for connecting telephone subscriber equipment to a telephone line, the circuit comprising: ring and tip connector means for connecting to telephone line ring and tip contacts and providing ring and tip signal outputs; a high impedance DC load and a gated line switch connected in series between said ring and tip signal outputs for controllably conducting an “off-hook” current between said ring and tip signal outputs; a transmit opto-coupler means having a transmit signal input and output; means for connecting said transmit signal output to said tip output and to a gate input of said gated line switch; means for controllably providing a low level DC bias signal to said transmit signal input and generating sufficient current on said transmit signal output to substantially saturate said gated line switch and seize said telephone line; means for providing an outgoing AC signal to said transmit signal input; and AC signal receive means connected to said ring and tip outputs for detecting an incoming AC signal and producing an incoming AC signal output.