The GPH-320C circuit is designed for years of trouble-free operation. There are no short-lived components to replace. The silicon rectifier assembly is rated for twice its normal operating voltage. The high-voltage regulated transformer is checked for freedom from corona. Conservative design throughout assures long trouble-free life, and close voltage regulation makes the GPH-320C insensitive to line voltage variations. The GPH-320C gauge is a single station gauge which indicates pressures on a three-range scale calibrated in units of dry air pressure. The basic gauge is available in 115VAC, 60 Hz. 
 
A solid state alarm or control circuit, GPH-010A, is available as an accessory. This circuit provides a set of relay contacts which can be preset (using a screwdriver adjustment on the rear panel) to open or close at any pressure throughout the range of the gauge. The trip point is independent of the position of the range selector switch. The control circuit plus into a connector on the printed circuit board inside of the gauge card and is easily installed on-site. Contacts for alarm or control functions (see specifications) are connected to a 3-pin plug which mounts on the real panel of the gauge.