Auxiliary air valve type indicators can also be provided in place of auxiliary electrical type contacts to provide complete isolation for main contact, and also auxiliary control answer-backs to indicate full open or closed, or for holding.

Units are also available for use in oil or insulating gases.  When placed in oil or insulating gases voltage ratings are increased up to 3 times.  Air exhaust outlets to exterior are provided to avoid contaminating the insulating fluids or impeding the cylinder action.  Units can be normally open or normally closed with loss of air pressure or can be semi-latching types requiring air pressure to move in either direction.

Typical E Series 
HV Air Operated Relay  
Model E15-NCP-15- 

They can be equipped with quick dump valves for faster action, or with ballast tanks or flow control valves for delayed action.

Manual or 3 way control solenoid valves for normally open or normally closed types and 4 way control solenoid valves for 2 operation can be provided in a variety of coil voltages as well as high voltage insulating type polypropylene air tubing rated to 250 PSI.   Moisture traps are also available if necessary.  Use of air pressure operating although usually slower than an electrical solenoid, provides faster action and longer life than motor operation and higher forces than solenoids. Use of air pressure allows the standard relay current range of 1ma to 200 AMPS also to be extended to a line of high current switches up to 36,000 AMPS continuous.