Network interface device and method

Pre-zero crossing signal generator for sinusoidal voltages...

Protected mechanism for DTMF relay

Redundant operation of ring voltage generators utilizing...

Ring signal generator for generating ring signals of different f

Ringer circuit

Ringing circuit

Ringing circuit for use in portable telephone set

Ringing generator for telephones

Ringing signal generator

Series ringing signal generator

Socket/plug in DTMF tone dialer

Software controlled ring voltage generator

System and method for providing particularized audible alerts

System and method for ringing other subscriber telephones...

Systems and methods for generating tones for operating...

T1 channel bank control process and apparatus

Telephone having an audio response function

Telephone interface circuit

Telephone line ring signal and DC power generator