Based on CMOS logic this short-circuit locator circuit uses the ear's ability to detect small changes in pitch, which are caused by variations in millivolts in a track under analysis.
This circuit detects the presence of a pilot flame in heating systems by the presence of infrared...
In the figure we have a circuit that uses unusual components, being indicated for low frequency...
Found in older Signetics documentation, this circuit generates signals from 30 Hz to 25 kHz....