This touch switch uses components that have easy-to-obtain current equivalents. The power supply must be isolated and the cable to the sensor must be short.
This output stage can directly excite a small speaker. The circuit is from a 1960 Mullard...
This rectangular signal generator was found in an Electronics World of 1966. The transistors are...
This protection circuit was found in a 1987 documentation. It consists of a relay that is...