This circuit was found in a 73 amateur radio magazine from the 90s. An LED extends the scale from 0 to 5 V to 10 to 15 V in this bargraph circuit. Other zener values can be used.
We found this circuit in a documentation for radio amateurs from 1977. The circuit can be changed to...
This is the complete circuit of a binary counter for educational purposes. Found in the February 1973...
This old circuit that makes use of germanium transistors, can be modernized with the use of...