Shunt regulator for hands free telephone

摘要

In a loudspeaking telephone the power supply to a loudspeaker amplifier (13) is shunted by a regulator (14) which functions as a programmable Zener diode. Under conditions of low available line current, e.g. where two similar instruments are operated in parallel at the end of a long line, the regulator voltage is reduced in value to disable the amplifier and conserve power to maintain the basic operating functions of the telephone.