Tuning system

Claim 1

In a tuning system for selected and tuning a channel signal selected from any one of a plurality of channel signals in the service area of the system; including a variable oscillator responsive to control signals for producing a local oscillation signal; means including a counter receiving signals from said variable oscillator for producing a count signal corresponding to the frequency of said local oscillation signal; means includng a memory for storing signals corresponding to the count signal desired when the variable oscillator is producing the proper local oscillation signal for the channel signal selected; and means including a comparator receiving both said count signals and the signals stored in said memory corresponding to the selected channel signal for producing said control signals for said variable oscillator whereby said variable oscillator will produce the local oscillation signal corresponding to the channel signal selected; and means mixing the local oscillation signal produced by said variable oscillator and a received channel signal for producing an intermediate frequency signal; the improvement wherein said memory additionally storing IF signals corresponding to the intermediate frequency signal, and control means are provided for receiving at least a portion of said intermediate frequency signal and comparing it with said IF signals stored in said memory for producing a second control signal varying said variable oscillator so as to hold said intermediate frequency signal constant, and circuit means for controlling said tuning system so that said control signals produced upon comparing said signals stored in said memory with said count signals are first produced to lock the variable oscillator on the local oscillation signal corresponding to the channel signal selected and then said second control signals are produced to hold said intermediate frequency constant.