# Contact selection on high and low pressure alarm switches

**URL:** <https://forumautomation.com/t/contact-selection-on-high-and-low-pressure-alarm-switches/53>\
**Category:** Pressure Measurement\
**Created:** [October 2, 2014, 5:34pm UTC](https://forumautomation.com/t/contact-selection-on-high-and-low-pressure-alarm-switches/53 "2014-10-02T17:34:15Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![instrumen](https://forumautomation.com/letter_avatar_proxy/v4/letter/i/65b543/32.png) [@instrumen](https://forumautomation.com/u/instrumen)\
**Post date:** [October 2, 2014, 5:34pm UTC](https://forumautomation.com/t/contact-selection-on-high-and-low-pressure-alarm-switches/53/1 "2014-10-02T17:34:15Z")

</div>

On a high pressure switch, the wiring is terminated on the “common” and the “normally close” contact terminals.

On a low pressure switch, the wiring is terminated on the “common” and the “normally open” contact terminals.

This type of contact termination is done to achieve a close contact from the switch during a normal (healthy) process condition which is a fail safe method.