Cradle switch bridge for telephone set

摘要

The cradle switch circuit, for a telephone set, consists of a bridge that is automatically adjusted in magnitude and phase by circuits comprising real and imaginary variable voltage-dependent impedances selected/controlled by FETs.A phase detector uses the 90 deg. -shifted voice signal as reference for producing the control voltage for the FETs. The advantage lies in being able to adjust both real and imaginary impedance.