This old 4-channel circuit was found in the December 1994 Electronics Now magazine. The circuit uses a 556 as a modulator. Note the code programming key.
This circuit has a start and reset switches and can generate signals at long intervals determined by the...
Found in a Popular Electronics from the 90s, this circuit uses a double 555 to emit beeps when the...
The components used in this 80's circuit are not common today. The circuit is very sensitive and must...