This circuit is from an article that teaches how to assemble it in the magazine Electronics Now from July 1993. It uses a liquid crystal display module from the time with 3 and a half digits.
Although indicated in the original publication of the 1980s as a capacitance switch, the circuit...
This amplifier step with a transistor has an input impedance of 100k to 10 M. The transistor can be any...
This circuit was obtained from an English magazine from 1977. The magazine no longer exists, but...