This circuit incorporates the passive control of the previous circuit and was also found in the March 1995 Electronics Now magazine. The power supply must be symmetrical.
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...