Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the Sonalert type with included oscillator.
Found in 90's Electronic Engineering, this circuit produces a pulse with a delay that depends on R3...
This circuit was found in the December 1984 issue of Radio Electronics magazine. The circuit has a...
Found in 90s Radio Electronics, this circuit is intended for amplifying analog video signals....