In order to facilitate the use of limit switch valves in applications where very low actuating forces and high flow rates are required, the Series 3 and Series 4 valves are equipped with new mechanical devices designed for this purpose. The Series 3 valve is designed with a mechanical lever which when operated releases an internal pilot signal to atmosphere. Actuation forces are less than 50g and the sensitivity can be increased by adding a “whisker” or rod of dia. 3mm to the lever.