Integrated Circuit System for Channel Selection of Varactor Tuned Television Receivers

The integrated circuits described in this paper were designed for electronic channel selection of varactor tuned television receivers. Two circuit types, hereafter called "analog voltage switch" and "logic control circuit", perform the essential functions necessary for channel selection and indication. Circuit partitioning and design were based on voltage breakdown, supply current requirements, circuit complexity, and a desire to package both circuits in 16 pin dual-in-line plastic packages. The logic control circuit consists of an oscillator which drives an up-down counter, logic circuitry which decodes the up-down counter and provides drive signals for the analog switches in an 8 ×2 array, automatic channel setting circuit, and an AFC defeat sound muting output. This circuit accomplishes channel selection by means of remote control or push-type switches. The analog voltage switch transfers the tuning voltage from the tuning potentiometers to the tuner and drives a high voltage indicating device such as a Nixie tube or neon bulb. Each analog voltage switch contains four switches to a common point and are cascadeable so the number of channels can be expanded in multiples of four to any desired number. However, the logic control circuit was designed to control sixteen channels and thus is used in conjunction with four analog voltage switches.