This circuit was found in Radio Electronics from the 90s. The sensor is an oscillator whose frequency depends on humidity, an uncommon component nowadays.
This circuit controls a heating element with voltage from 6 to 30 V and current up to 3 A from...
We found this Vox in a 1969 Motorola documentation. Transistors support modern equivalents and the SCR can...
Found in a 90s Elektor, this mixer makes use of integrated circuits of the time. The supply must be...