This alarm with automatic shutoff was found in the April 1975 Radio Electronics magazine. The activation time is given by C1 and R3. The alarm uses series and parallel sensors.
We found this junction tester circuit in an old English documentation. The circuit serves to check...
This circuit can generate signals up to 100 kHz. Found in documentation from the 1980s, it makes...
Found in American documentation from the 70s, this circuit uses components of the time, uncommon...