Found in American documentation from the 1980s, this circuit makes use of components of the time, which are uncommon today. The circuit detects the approach using a sensor formed by metal plates.
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...