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 infrared emitter (pulsating) can be used with several other alarm and remote-control circuits on...
Signals of up to a few tens of kilohertz can be generated by this circuit found in a European...
This amplifier was found in a technical documentation from the 1970s. The circuit uses 2N2218...