We found this frequency meter circuit in a 1974 documentation. The circuit is powered by 12 V and has 8 digits. Changes can be made using a prescaler to reach higher frequencies.
The original purpose of the figure circuit, suggested by National Semiconductor, is to keep the...
The amplifier shown in the figure was obtained from the Anlog Devices linear integrated circuits...
When the sensor X1 is opened, the relay is energized. When waiting, the current drained is very...