While the electrical contacts are typically SPST (Single Pole Single Throw) and reversible for simple switching

The Johnson Controls P499RAP-101 is a high-accuracy electronic pressure transducer designed for mission-critical HVACR applications

When performing a vertical HVAC unit repair

It manages the timed operations of the HVAC cycle

Zero Minimum Pressure: Operates reliably at 0 PSI inlet pressure

Tekmar Controls 304P Relay Panel 322838-753 While the electrical contacts areThe Tekmar Controls 304P Relay Panel is a professional grade 4 zone switching relay engineered to manage up to four low voltage thermostats and four 120V circulating pumps in hydronic heating applications. Built for technicians who demand reliability in zoned radiant floor or baseboard systems, this hydronic zone control utilizes a microprocessor based design to coordinate calls for heat with precision. The 304P switching relay features RoomResponse