This old fashioned transistor amplifier was found in a publication of the year 1958. Transformer are the critical components in the circuit and power comes from 6 D cells.
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...