Found in a 1968 Mallory documentation, this circuit makes use of an integrated circuit of the time.
Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the...
This circuit was found in a General Electric documentation from 1970. It is used in an optical...
This circuit can switch signals in the 3.5 to 30 MHz band. We found it in a QST magazine from the...