This is a replacement air switch from Tecmark formerly called Tridelta. This air switch was used widely in many brands of spa control packs; like Hydro-Quip, Brett Aqualine, CRL, Hercules, Hurricane and many others.

This is a "latching" air switch which means that it will make a contact when activated by the air button and maintain that contact until the air button is pressed again.

This Tridelta TBS-301 air switch has SPDT (single pole double throw) electrical connections.