Found in old documentation, this circuit uses a double gate MOSFET. The operating frequencies depend on the coil, and the indicator is a microammeter.
This circuit detects signals in a wide range of frequencies, indicating their strength in an...
This traditional two-tone alarm configuration with the 4011 integrated circuit was found in a 1998...
This circuit was found in the June 1980 issue of Radio Electronics magazine. The circuit uses an...