A system for transmitting hydraulic control signals and hydraulic power to downhole well tools while reducing the number of hydraulic lines installed in the wellbore. Hydraulic control signals can be furnished at relatively lower pressures, and the hydraulic pressure within the line can be selectively increased over a threshold level to provide hydraulic actuation power. The system can provide multiple control paths through a few number of hydraulic lines to provide flexibility and verification of well tool operation. Closed loop hydraulic operation monitors well tool operation, and a combination of pressurized hydraulic lines can provide an operating code for selective downhole well tool control. Four hydraulic lines can provide independent control and actuation of seven well tools, and additional combinations can be constructed.