Realistic steam-sound generator is easily installed in HO Scale or larger models. Circuitry has individually controlled accurate "chuff" sound with constant background hiss. Self-contained SS-1 is powered by a 9V battery and may be used with any form of track power. Includes 1 x 1 x 1/2" circuit board, 9V battery holder, subminiature slide switch, 1" diameter speaker, volume-control resistors, chuff contact wire, insulating material and complete instructions.