This circuit was found in a 1967 Japanese documentation. It consists of a touch control system with two transistors from the time. The circuit uses a power source and sensitive relays.
This circuit for vehicular use is from an 80's American publication. The circuit has a light...
This circuit was obtained in a manual of operational amplifiers of 1973. The circuit uses...
This circuit, from a 1978 publication, can be made with more modern transistors such as the TIP42,...