The Model 840 is designed for use with the CANNON BALL EXPRESS & ORIENT EXPRESS Train Horns or any high-pressure horns that require an onboard air system. Designed with a special extended tank 5.5 liter and a heavy duty, high volume compressor. Will sound the CANNON BALL EXPRESS horn for ten seconds of continuous sound. The Model 840 is a simple two-piece air supply system consisting of a metal storage tank, compressor, 10 ft. of ¼" air hose, brass fittings and mounting hardware. The TURBO compressor is balanced an has heavy rubber bushings in it's mounting base to virtually eliminate all vibration and the tank has a built-in pressure regulator to maintain 110 psi in the tank.