TWO WIRE TELEPHONE APPARATUS IN SPEAKER PHONE

摘要

A speaker phone preventing the howl and making a call to each other simultaneously consists of A part and B part. The amplifying transmitter(TA1) consists of TR1 connected to output of the TA1 through TR3 and a coupling condenser(C1), TR2 which output is connected to A1 tap of communication line(C) through diode(D1). The system of receiver(RA1) is same as the transmitter except to have reverse polarity in transisters(TR5-TR7), diodes(D3,D4) and power source.