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.
This circuit was obtained from an English documentation based on a 74121 TTL integrated circuit....
This circuit generates signals with opposite phases determined by C1 and adjusted by R2. The...
The presented circuit uses two old germanium transistors. We found this configuration in a...