Found in documentation from the 1990s, this circuit uses an integrated radio from the time and has high impedance earphone listening.
This circuit was taken from the 1974 Ferranti transistor manual. Transistors are common types at...
This circuit monitors the current of a series of 40 V lithium battery packs connected in series....
This 1970 Philips circuit uses a mechanical counter. The circuit is triggered by a reed switch...