Found in American documentation from the 90s, this circuit can measure frequencies on a linear scale from 0 to 1 kHz. The components can be changed to measure other ranges.
Using the 2N2646 this circuit was found in a Radio Electronics magazine from July 1968. The...
The purpose of this circuit found in a 1990s Popular Electronics is to increase the current...
Found a documentation for PC from 1992, this circuit is indicated for the English power grid of...