Obtained from a 1969 documentation, this circuit can operate at frequencies up to 500 Hz, counting up to 999. The circuit makes use of neon lamps of the time.
We have several circuits like this on the website. What it does is generate a signal in the range...
Found in American documentation from 1968 this circuit is based on discrete components in addition...
By connecting several photocells in series, we can directly activate a sensitive relay, as shown in...