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 is found in documentation from the 1990s. The load can be a relay and the sensor, an LDR of...
This oscillator can run in frequencies up 10 MHz depending on the Power supply voltage. The 1 µF...
This circuit was found in an old Popular Electronics. It causes an LED to pulse and, at the same...