An Approach to Ultrasonic Remote Control Systems

Remote control systems for television receivers have, in general, tended to fall into the category described by the block diagram shown in Figure 1. This usually consists of an ultrasonic CW generator which transmits a specific frequency to the receiver for each control function required. The receiver system comprises an ultrasonic pick-up transducer and amplifier feeding the received signal to a series of tuned band-pass amplifiers, one for each frequency. The detected signal is then used to activate the desired control function. The signal frequencies employed are in the 30 to 50kHz range. Some of the problems with this type of system include range and directionality of the transmitter, receiver response to spurious inputs, e. g. coin/key noises, and the complexity of the receiver circuitry and its alignment. It is to this latter problem that this paper principally addresses itself.