With a mains-rated transformer and 1:1 winding this benchtop circuit was found in the January 1995 issue of Electronics Now magazine.
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...