VCO frequency setting to manually chosen frequency - uses counter and has control loop integrator reset automatically

摘要

The frequency setting circuit, for setting an electronically tuned oscillator to a frequency selected by hand, counts the oscillator output frequency and compares it with a reference to produce a control signal for applying to the oscillator via an integrator. - Only those counter outputs (Z) that form part of the digits of the last decade and that contain the same digits as the required digit (S) are connected to the comparator (D). The counter outputs for the remaining digits (S+ 4 etc.) are connected to an electronic switch (M) that resets the integrator to its starting value. The tuning loop responds faster than the oscillator tunes but slower than it drifts. The advantage lies in automatically resetting the integrator.