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.
This circuit can use a pendulum sensor. We found this configuration in a 1994 publication. The...
This circuit is from a 1964 Electronic Design. The sensor is an LDR and the transistors are...
This circuit works both as a preamplifier and activates a relay when speaking in front of the...