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 American magazine in 1978. It activates a relay when the speed of a...
This second-order low-pass Salen-Key filter was obtained from an American 1980s documentation. Formulas...
The circuit shown in figure 1 generates an intermittent tone in a piezoelectric transducer when...