Abstract: A system for transmitting hydraulic control signals or hydraulic power to downhole well tools while significantly reducing the number of hydraulic lines required. Hydraulic control signals are furnished at relatively low pressures to actuate a selected well tool, and the hydraulic pressure is selectively increased over a threshold level to provide hydraulic power to the well tool. The hydraulic control actuation signals can be controlled by selectively pressurizing different hydraulic lines in a selected sequence and by selectively powering the fluid pressure within a selected hydraulic line. The combination of selective sequential actuation and selective fluid pressure provides multiple actuation combinations for selectively actuating downhole well tools. Additional combinations can be provided by changing the pressurization sequence, magnitude, absolute time, duration, and pressurization profile within a discrete time period.