This circuit was found in the July 1986 issue of Radio Electronics magazine. The circuit has a loudspeaker warning system. The sensor is the ceramic capacitor C1 which acts as a transmission line.
This circuit compensates for the brightness of an LED as a function of temperature. We found it in...
This very sensitive circuit works almost like an electroscope. The FET can be the BF245 and it...
Constant currents from 10 mA to 1 A can supply the load, depending on the selection made by S1. Q1...