ELECTRONIC INTERNAL LINE AUTOMATIC TELEPHONE SYSTEM

Disclosed is an electronic internal line automatic telephone system, comprising a telephone set, a cable and an energy source. The utility model needs no additional telephone exchange or operator, and the capacity is 12 door which can be expanded into the maximal 36 door. The numerical selection element circuit of the telephone is a CMOS self locking bistable switching circuit. The electronic ringing circuit is an 8024CMOS special integrated ringing circuit with the direct current power supply of 24 volts. The telephone set is connected with the energy source through the multi-core cables twisted by bifilar polyethylene insulation shielded by aluminum foil. The utility model has the advantages of dialing, busy showing, ringing displaying, talking confidence, little cross talk, beautiful bell, power saving, long communication distance and convenient maintenance, etc.