This is a typical 3 ½ digit TTL counter. We found it in the September 1973 issue of Radio Electronics magazine. The circuit is to be powered by 5 V. It can be expanded to more digits.
Found in Radio Electronics from the 90s, this circuit uses components from that time. However, it...
We found this circuit of a clamp-type ammeter in a Japanese documentation from the 1960s. The...
This circuit was found in a 1965 General Electric documentation. It is intended for reception of the...