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
Telephone line seizure circuit
Telephone line switch using an optocooupler
Telephone on-hold device
Telephone plug system
Telephone power supply
Telephone privacy device
Telephone receiver circuit with dynamic sidetone signal...
Telephone receiver transmitter device