Now is a good time to explain some of the terminology used with Pressure Switches in order to help you with your selection.

Single Pole Double Throw (SPDT) With this type of switch the electrical circuit can be "made" when the switch is activated (common to N.O.) or "broken" when the switch is activated (common to N.C.).
Single Pole Single Throw (SPST) Normally Closed With this type of switch the electrical circuit will be "broken" when the switch is activated.
Single Pole Single Throw (SPST) Normally Open With this type of switch the electrical circuit will be "made" when the switch is activated.
Deadband/Hysterisis/Differential are all terms used to describe the difference between when a switch activates and when it resets. Because of the mechanics of the micro-switch this is seldom at the same setting. Some of our switches have fixed deadbands (Series PMM, VCM, TB) and others have limited adjustable deadbands (Series PSM, PSP, VSM).
Set Point is the setting at which the switch will activate. Series TB is the only switch that does not have an adjustable range for selecting the set point.