Re: How to hook up Nason pressure switch
 

Alan,
In this case "common" refers to a physical part of a switch rather than power supply. Is it rarely used in a single pole single throw switch but may appear on switch bodies that are used for many different products. Depending on the designer and the circuit used, the "common" terminal could be connected to the power supply rail.

Re: How to hook up Nason pressure switch
 

Ah, thanks a lot everyone!