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.
This circuit is from an August 1984 Radio Electronics magazine. It monitors the state of a RAM...
In the figure we have the way to obtain an adjustable constant current source of 2 mA. The...
Found in a Maxim publication from the 90s, this circuit generates signals from 10 to 25 kHz with a...