The HYRAD Technology is a patented method for adjusting shocks and struts
remotely. HYRAD Corporation holds three U.S. patents and many foreign patents
on the use of 
external
fluid pressure circuits to adjust the valving (firmness) of shocks and
struts by remote control. The control fluid can be either a gas or a liquid.
Compressed air has proven to be a convenient medium for this purpose. Shown here is a photo of a basic pneumatic control system. From the control panel, the driver of the vehicle can touch a button to turn on a miniature air compressor that builds pressure in the control lines and stiffens the shocks. Or, the driver can touch a bleed button that lets air out of the control lines and softens the shocks. The compressed air does not pressurize the shock absorber. It simply acts on an adjusting piston to "shift" the valving. The gage on the control panel shows the level of damping that has been selected. It's like having five different sets of shocks on your vehicle! Push a button to select the "set" you want!
A schematic diagram shows both the pneumatic and electrical circuits:
