Found in a 1966 documentation, this “coin finder” uses components from the era operating at 2.1 MHz. The circuit uses an audio amplifier for detection.
We found this circuit in a 73, magazine for radio amateurs of the 90s. The circuit is passive and...
This configuration for proper connection of parallel amplifiers was found in National...
We found this circuit in a 1965 General Electric documentation. The circuit generates synchronized...