The 506 Double-Acting Bell Ringer is the standard in the North American locomotive industry for reliability and performance. The clapper is designed to strike the bell on a continuous or intermittent basis as controlled by the operator with our 616 Operating Valve or through some automatic means as developed by the Original Equipment Manufacturer. Unlike earlier technology, the 506 incorporates a unique "dual-action" motion of the integral pneumatic motor and piston. As a result, the clapper swings free with no return thrust or force on the piston resulting in longer life. The pneumatic motor and piston is a cartridge like mechanism that may be changed quickly without breaking any pipe connections or using special tools.