Found in an EDN from the 1980s, this circuit uses a double 555. The circuit activates a relay that controls a horn or siren. Next to the diagram we have the timings.
This circuit was found in the February 1980 issue of Radio Electronics magazine. The digital...
Found in a Popular Electronics from the 90s, this circuit is intended to measure the harmonic...
This circuit that simulates the sound of a drum is part of an article published in the Radio...