This TTL circuit is from a Radio Electronics magazine from November 1983. The circuit drives a set of LEDs. The integrated circuit used is a BCD to decimal decoder.
This is a Japanese commercial circuit found in a 1967 documentation. The transistors are from the...
This circuit was found in a Radio Electronics from October 1952. The circuit equalizes the sounds...
This circuit is from an old American publication, but it can be easily implemented with modern...