20 Hz ring generator using high frequency PWM control

Active decoupling and power management circuit for...

Apparatus for sending a ringing signal and data with reduced...

Automatic volume control for a telephone ringer

Change to playback characteristic of ringback tone

Combine audio and ringing mode

Computer with a modem capable of outputting telephone bell...

Counter based ringer interface

Current limited electronic ringing generator

Differing frequency sine wave generation from a look-up table

Direct drive for a subscriber line differential ringing signal

Direct drive for a subscriber line differential ringing...

Isolated drive circuit

Low power emergency telephone mode

Method and apparatus for controlling a telephone ring signal

Method and apparatus for DTMF detection

Method and apparatus for generating a ringing signal

Method and apparatus for ringing telephone stations

Method and system for implementing a ring back tone based on...

Method of processing phone dialing/redialing function and...