SSD61.5U Building Technologies Valve Actuators, SSD Series. Pressure Independent Control Series SSD Electronic Valve Actuators require a 24 VAC power supply and receive a floating control signal (SSD81…) or a proportional 0 to 10 VDC signal (SSD61…) to control a valve. The 0 to 10V SSD61U actuator also accepts a 24 VDC power supply. These actuators are designed to work with 1/2‑ to 1‑1/4 inch normally open and normally closed Pressure Independent Control Series Valves with a 2.5 mm or 5 mm stroke and a threaded valve bonnet that fits the actuator.