This circuit was presented in a January 1990 Radio Electronics magazine article as part of a home theater sound effects system. It consists of a 3 kHz high-pass filter.
Suggested by Raytheon in 1967 documentation this circuit uses a lightbulb and LDR optical coupler of the...
Found in American documentation from the 90's, this circuit consists of a solid state relay with...
Indicated to be used at the sensor input of a PC, this circuit was found in an English...