This circuit uses two stages of transistors to make a circuit that can be activated by touching two points. The momentary switch and the 200 kilo-ohm resistor simulates your skin contact between ground and the 10 kilo-ohm resistor. The 10 kilo-ohm resistor is present in case the leads off the real circuit were connected directly together in order to prevent an inrush of current into the base of the transistors. As an added note, skin resistance isn't the same all over the body, or from person to person. Feel free to change the 10 mega-ohm resistor to see how wide of a resistance can be used before the output is affected.
