Wolo's NEW PHILLY EXPRESS. The four trumpets and mounting base are metal triple chrome plated and designed smaller to fit into engine compartments that are unable to accommodate a full size train horn. Built into the horn's base is a heavy-duty, chrome plated 12/24-volt electric solenoid valve. The PHILLY EXPRESS requires an on-board air system, (recommended Wolo on-board air system Model 800). Comes with all mounting hardware.