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.
This circuit was found in 1980s Electronic Engineering. Transistors can be modern equivalents. The...
In this National Semiconductor circuit, the output voltage is numerically equal to the square root...
Found in documentation from the 1980s, this circuit uses an operational amplifier from that time....