Search circuit for a radio receiver

Abstract

A search circuit is provided for sequentially activating selected local oscillators to cause a radio receiver to receive the radio frequency channel corresponding to the frequency of the activated local oscillator. The search circuit provides repetitive pulses which are passed through a skip circuit and are then decoded in sequence. The decoded signals are applied to respective local oscillators and are also applied to respective memory circuits. Each memory circuit can be preset with a scan or a skip memory signal. If preset with a scan memory signal, a memory circuit produces a constant scan output. If preset with a skip memory signal, a memory circuit produces a skip output each time it receives its respective decoder signal. All of the memory circuit outputs are applied to the skip circuit. Each memory circuit which produces a scan output causes the skip circuit to pass the repetitive pulses through without change. Each memory circuit which produces a skip output causes the skip circuit to provide a short duration, additional pulse between the repetitive pulses. This additional pulse causes the next decoded signal in the sequence to be produced, thus skipping a channel.