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.
We found this circuit in a 1994 Linear Applications Handbook by National Semiconductor. The LM10...
This is an amplifier for recorder and return containing preamplifier and power amplifier with...
This S-meter circuit was found in a 1976 publication. The circuit is used to measure the signal...