This protection circuit was obtained in a 1969 Electronic Design. The SCR can be the current equivalent, depending on the fuse current.
This 1967 Philips circuit recognizes a light signal (visible or infrared) modulated by tone. The...
This circuit makes use of the LM11, 112 or 113 operatives and was found in a 1980s documentation. The...
Found in a 1969 Ferranti documentation, this circuit uses only bipolar transistors from that time....