Automatic tuning of TV or radio receiver - has oscillator output digitally compared with reference to provide adjustment of frequency

摘要

A fully automatic timing system for television or radio receivers is based upon a timing-remote-digital(TRD) technique. The output of the timing oscillator (1) is divided by a ratio of 2,048 over two stages (4, 6) and changes the state of an up-counter (18) to provide a measured value for comparison (14) with the required frequency provided by a ROM (16). An arithmetic unit (15) provides a signal difference that is converted by a D/A (10) to control the oscillator (1) to lock onto the required station.