This circuit is from an American 1964 documentation. Transistors of the time are used, but modern equivalents can be employed.
This circuit with 3.3 MΩ input impedance was found in the October 1993 issue of Electronics Now...
We found this circuit in a 1967 Electronic design. However, it can be easily implemented even...
The purpose of the circuit shown in the figure is to open and close the contacts of a relay...