The 106-RPS-D and 206-RPS-D pressure differential sustaining valves are based on the 106-PG or 06-PG main valve.
The RPS-D uses the 81-RPD pilot valve and has two sensing connections. The valve and pilot remain closed until the difference between the two pressures exceeds the pilot setting. Under flowing conditions, the pilot reacts to small changes in pressure to control the valve position by modulating the pressure above the diaphragm. The pilot setting establishes a differential pressure that is held relatively steady despite changes in system pressure or flow.
For more information on the 106 / 206-RPS-D pressure sustaining valve: