This UE united electric J300-554 pressure switch, 0-30 PSI, 125/250 VAC, 1/4" is a sensor/switch. It senses object presence, distance, or position (or switches an electrical circuit) and converts that into an output signal for machine control or monitoring. Key specifications noted on this listing include 250 VAC, 30 PSI. It is commonly in process monitoring and machine safety or positioning applications.
