This is a diagram of a 1970s reel or tape recorder. It is an Italian Geloso recorder, quite popular at the time. The circuit is a reference for equipment recovery.
This flood or humidity alarm was found in an English publication in 1991. It can still be fitted...
This simple transistor tester uses a common 3 mA analog instrument that has its scale changed as...
This RF amplifier step has a dynamic range of 140 dB and can amplify signals from 0.5 to 40 MHz....