Digital Remote Control System

Abstract

A digital function selection system for ultrasonic remote control of TV sets uses pulse counting techniques with the 60 Hz line frequency as the time base. The system achieves superior noise immunity with a unique "Confidence circuit," which uses an adaptive sampling technique to insure that a valid ultrasonic signal is being received. This prevents extraneous random ultrasonic noises present in the environment from causing any function to operate. This technique is superior to other systems in that it processes in-band as well as out of band interference. Upon receiving a valid ultrasonic signal, the I.C. decodes the signal to achieve two way channel control, eight step up-down volume, TV power on/off and mute on/off. A hysteresis circuit on the I.C. reduces the tendency for noise spikes on the 60 Hz line to affect the time base. An option pin enables the system to have either an eight step up-down volume control or a bistable function and four step one way volume control. The I.C. is implemented using p-MOS technology. This paper covers the design of the entire system with special emphasis on the digital integrated circuit.