This kit combines a touch switch and a touch plate, both built onto one PCB so you can see and explore how each type works. A battery can power the touch switch (2 contacts) but a +12V power supply (not included) must be used for the touch plate (1 terminal) to work. A high quality 12V relay rated at switching 240V/3A is supplied. This very simple circuit uses a 4011 (or 14011) CMOS NAND gate as the input detector.