This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit uses a unusual optocoupler that can be replaced with an equivalent one.
This is a very common circuit in the days of xenon flashes for cameras. This is from a Radio...
This circuit uses a resonant reed relay to recognize the frequency of an input signal. Adaptations...
This circuit controls the passage of the signal from an input to an output using a DC signal from a...