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.
In the figure we have a simple logic level indicator for TTL circuits or powered by 5 V....
This circuit was obtained from the December 1990 issue of Radio Electronics magazine. The circuit...
This power supply for gas laser (HeNe) was found in a 90’s Popular Electronics. It generates from 1300...