This valve provides a means of sensing the higher pressures between two lines on a hydraulic circuit allowing this line to be used for an auxiliary function such as the removal of a mechanically applied brake, the operation of a gauge or to give a remote pressure sensing line for the control of a separate valve.

When a higher pressure is sensed at Port 1 than at Port 3 the ball within the cartridge is forced against a seat closing Port 3, opening Port 1 to Port 2. When the higher pressure appears at Port 3 the ball is forced against the seat at Port 1 and opens up Port 3 to Port 2.

Cartridge design enabling speedy servicing when mounted in a body or in a composite manifold.