This circuit was found in the September 1992 issue of Radio Electronics magazine. The circuit does not use a transistor to drive the relay and has no adjustments.
This circuit converts pulse frequency to current, which is indicated on an analog instrument. The...
August 2017 - TPS4H00EVM Power Module Modules for Texas Instruments High Power Positive Side...
This circuit was obtained from Dutch documentation from 1964. The components are of the time, but...