Signal-seeking tuning system with automatic bandswitching for a television receiver

A signal-seeking tuning system for scanning a plurality of radio frequency (RF) signal bands, each of which bands includes a plurality of channels in which RF signals may be present, for selecting present ones of said RF signals, which tuning system comprises:

• tuning means, responsive to a tuning signal and to one of a plurality of band signals, for selecting and heterodyning a present one of said RF signals to produce an IF signal having a nominal frequency;
• signal processing means receiving said IF signals, and including means for applying a control signal to said tuning means to fine tune said IF signal to said nominal frequency;
• a source of clock signals;
• means for selectively developing an up signal and a down signal;
• digital counter means for generating a binary word having minimum and maximum values, said binary word increasing in value in response to said clock signal and said up signal being applied to said counter means and decreasing in value in response to said clock signal and said down signal being applied thereto, said binary word changing cyclically between said minimum and said maximum values;
• converting means coupled to said counter means for developing said tuning signal responsive to said binary word;
• register means for developing said band signals in a predetermined sequence;
• first means coupling said counter means to said register means for causing said register means to develop the next band signal in the order of said sequence when said binary word increases to reach said maximum value;
• second means coupling said counter means to said register means for causing said register means to develop the next band signal in the reverse order of said sequence when said binary word decreases to reach said minimum value;
• and
• detecting means for stopping said counter means from changing the value of said binary word when said IF signal has a predetermined condition.