The 232 Frequency Detector is a collection of circuits to generate a CV and sine wave output that track an incoming signal over a frequency range of 80 Hz to 2500 Hz. This module was designed to track an acoustic instrument or human voice and provides a CV, Pulse, sine wave output with a transfer gate for envelope control. 

The signal leveler is an automatic gain control (AGC) circuit which provides a constant amplitude signal for processing. It also contains a 60 Hz notch filter and a tracking bandpass filter. A reasonable input signal level is about 500 mV pk-pk indicating more of a traditional line level input from a preamplifier output. The constant amplitude signal begins to distort about 1V pk-pk input.

The tracking filter reduces the input signal to its fundamental frequency. The frequency detector generates a CV which drives a phased locked VCO which tracks the fundamental frequency to provide the locked oscillator output.

The output of the tracking filter also drives an envelope follower with a threshold level which generates a trigger/gate (pulse) output. The internal gate also drives a track & hold (sample & hold) on the CV output. Use of the track & hold allows the module to hold the last valid CV when the input signal disappears and the locked oscillator drifts.An independent transfer gate is also controlled by the envelope detector. The. locked oscillator if patched, or other external signal, can be processed by the transfer gate to follow the input envelope including muting when the input signal is removed.