This circuit was obtained in an American documentation from the 80's. The transistors can be equivalent to those indicated and the crystal can reach a few tens of megahertz.
This circuit can be implemented with standard photodiodes consisting of a two input optical AND gate....
This TTL counter was found in the March 1991 issue of Radio Electronics magazine. The circuit is...
The circuit shown in figure uses a photodiode as a sensor element and its main feature is to have...