Telephone having separate power circuit for supplying power to s

Telephone headset amplifier and method of operation

Telephone headset amplifier with battery saver, receive line noi

Telephone headset amplifier with battery saver, receive line noi

Telephone headset amplifier with noise blanking capability

Telephone headset in-use indicator

Telephone headset interface circuit

Telephone hold circuit

Telephone in-use indicator

Telephone indicator system and method

Telephone instrument

Telephone instrument and method for altering audible characteris

Telephone instrument and method for altering audible characteris

Telephone interface circuit with impedance termination during ca

Telephone interface for simultaneous audio presentation at separ

Telephone line current modulator

Telephone line hold and hold release apparatus

Telephone line interface

Telephone line monitor amplifier

Telephone line noise filter apparatus