Highpower Security 750 Pneumatic Timers are miniature momentary time delay switches for OEM applications. Pressing the switch button, or push plate (when used in an assembly) actuates the switch’s contacts. These contacts stay actuated for a set time delay, which is adjusted using the brass knob at the back of the switch. Turning the brass knob controls an internal flow of air that regulates the time delay. These pneumatic timer units are used in many switch assemblies for security and industrial control applications.