Power saving circuit in pneumatic valve
The valve works by attracting an iron armature into a solenoid. This means that when un-energised, there's a large airgap in the magnetic circuit. When it's energised, the airgap is much smaller.
The large initial airgap means that a large current is required to develop enough force to move the armature. When the airgap is smaller, less current is needed to develop the same force.
The power saving circuit appears to be integrated into the valve. When you apply power to the valve from your control, the timer circuit turns the transistor on, which applies the full voltage across the valve coil. After a while, during which it's assumed that the valve has pulled in, the timer circuit turns the transistor off, and the coil is now only supplied through the resistor. This lowers the voltage to the coil, causing it to draw less current, but still enough to hold the valve on.
This is a quite inefficient method of doing it. Had they used a buck converter instead of the resistor, then the power consumption could be reduced yet further, albeit at a higher cost for components.