Control method wherein communication signals are conducted to the subsea system and used to open or close electrically-controlled hydraulic control valves. NOTE Hydraulic fluid is locally sourced and acts on the associated subsea valve actuator. “Locally sourced” may mean locally stored pressurized fluid or fluid supplied by a hydraulic umbilical line. With electrohydraulic control systems, data telemetry (readback) is readily available at high speed. Multiplexing of the communication signals reduces the number of conductors in the umbilical.
Source: API SPEC 17F, Specification for Subsea Production Control Systems, Second Edition, December 2006 (Reaffirmed April 2011). Global Standards