Broadcast receiver tuning circuit with station memory

Claim 1

In a tuning circuit for a high frequency broadcast receiver, which circuit includes a voltage controllable superheterodyne oscillator arranged to receive a control voltage and to produce an oscillation whose frequency is determined by the value of the control voltage and determines the broadcast frequency to which the receiver is tuned, a counter connected to sense the frequency of the oscillations being generated by the oscillator and to produce therefrom a count state in the form of representations of the digits of a first decimal number identifying the broadcast frequency to which the receiver is currently tuned, input means for generating representations of the digits of a second decimal number identifying the broadcast frequency to which it is desired to tune the receiver, a circulating memory having a plurality of memory cells, including a memory input cell and a memory output cell, for storing a succession of digit representations and having an input connected to the input means for receiving the representations of successive digits of the second number and a feedback path connected for causing the representations in the memory output cell to be conducted back to the memory input cell and a comparison circuit for comparing the decimal number representations being produced by the counter and contained in the memory to vary the control voltage in a direction to cause the number representation produced by the counter to coincide with the number representation generated by the input means, the comparison circuit including a single comparator capable of comparing, at one time, only the representations of one digit of each of two numbers, and time multiplex means connected for delivering to the comparator, in succession, each digit representation produced by the counter, starting with the most significant digit, and, simultaneously therewith, each digit representation of corresponding significance generated by the input means, the improvement comprising: a station memory for storing the digit representations completely identifying at least one broadcast frequency, means for selectively connecting said station memory into the feedback path of said circulating memory in a manner to permit transfer of data between said memories; an input unit actuable for providing signals identifying particular station memory locations and initiating a station memory write-in operation; and a logic linkage circuit connected between said input unit and said station memory for selectively writing digit representations currently in said circulating memory into particular station memory locations or reading into said circulating memory digit representations previously stored in particular station memory locations.