Found in American documentation from the 1980s, this circuit makes use of components of the time, which are uncommon today. The circuit detects the approach using a sensor formed by metal plates.
This phase shift oscillator generates sinusoidal signals in the audio range. Frequency depends on...
This circuit, from an old Argentine publication, makes it possible to use a 1 mA full-scale...
This circuit is from a 1967 documentation. It makes use of varicap and diode tunnel in addition to...