This 1965 circuit uses a Philips 4068 tube to measure extremely small charges. The circuit has as indicator a micro ammeter and the transistors are of the time.
This circuit consists of a simple capacitance bridge. The handset can be high impedance from 500...
This simple wireless microphone circuit for the MW band was found in an old American...
This astable with active cycle adjustment was found in a Popular Electronics from the 90's. The...