This counter was found in the November 19983 issue of Radio Electronics magazine. The power supply can be between 3 and 12 V typically. The counting speed depends on C1.
We found this circuit with a Q factor of 25 in the Linear Applications Handbook by National...
Found in a 1967 Electronics World, this preamplifier uses an integrated circuit from that time,...
This circuit uses a special 1950's RCA strobe tube. It can be built with equivalent components for the rest...