Frequency lock-in preset tuning system

Claim 1

A preset tuning system, comprising a control voltage source, a search tuning circuit having an input and an output, said search tuning circuit including a ramp generator circuit for generating a predetermined and reoccurring voltage ramp and a frequency locking circuit, tuning means having an input coupled to said search tuning circuit output and an output coupled to said search tuning circuit input; said tuning means being tuned by the amplitude of the voltage on said search tuning circuit output generated by said ramp generator circuit, said frequency locking circuit having means for sensing a signal on said search tuning circuit input, for locking on the center frequency of that signal, and for alternatively inhibiting and initiating operation of said ramp generator in accordance with the center frequency of the sensed signal whereby the tuning of said tuning means is maintained at said center frequency; means for removing the signal on said search tuning circuit input whereby said ramp generator is no longer inhibited; means to temporarily inhibit said search tuning circuit while simultaneously and temporarily coupling said control voltage source to said search tuning circuit output, said tuning means being adjustable by said voltage source to a desired frequency signal while said ramp generator is inhibited, whereby said frequency locking circuit coincidentally detects the center frequency of said desired frequency signal and permits limited operation of said ramp generator when said search tuning circuit is no longer inhibited and said control voltage is no longer coupled thereto, to maintain the tuning of said tuning means at the center frequency of said desired frequency signal.