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 was found in an old European documentation. When R2 is cut off the circuit triggers...
This 45 to 90 Hz hum elimination circuit was obtained from a 1980s documentation. The operational can...
This circuit was found in a 1989 documentation and was intended to be part of a presence...