The 1651C2S Displayless Pressure Controller is a self-tuning controller which operates from user-supplied ±15 VDC input power. Its compact size allows for installation anywhere on the process system, saving valuable rack space. The 1651 can be commanded through RS-232 communications, or it will accept an analog set point for pressure or position control. Alternately, there are five preprogrammable pressure or position set points which can be selected via TTL signals. It is fully compatible with the electrical signals, connectors, and software of the MKS 651 Controller. The self-tuning algorithm determines optimal control parameters for any set point in the range of the valve by learning time constants, transfer functions of the valve and plumbing, valve gain, and other important parameters.