This touch-actuated switch stays on as long as you keep your finger on the touch plate. Rl sets the input impedance to a high 22 MO. Ql picks up stray signals coupled through your body to the touch plate and amplifies them to tum on Q2, which turns on lamp drivers Q3 and Q4. Lamp 11 is any small12-V lamp, such as a No. 53-12 V 120 mA. R4 and Cl add a small amount of hysteresis (delay) to keep the light from constantly flickering.