Found in a 90s Popular Electronics, it serves both TTL and CMOS logic. The injector can provide 10 kHz or 100 Hz signals. The circuit drives a transducer and two LEDs.
Also suitable for use as a noisy alarm, this Morse Code or telegraph practice oscillator was found...
This differentiating circuit applies to any operational amplifier. It operates with the negative...
This alarm circuit was found in a 1997 publication. It uses two reed-switches to arm and disarm the...