CIRCUIT FOR SUPPLYING CALLING CURRENT IN SUBSCRIBER INTERFACE MODULE

摘要

PURPOSE: A circuit for supplying a calling current in a subscriber interface module is provided to prevent saturation phenomenon of a transformer by a DC which flows in the transformer. CONSTITUTION: Feedback resistor units(R21,R22) receive a -48V input power and supply a uniform DC. A transformer(23) connects to the feedback resistor units(R21,R22) in parallel, and transforms the voltage outputted from the feedback resistor units(R21,R22). PTC thermistors(21,22) increases temperature and resistance.