Editing Emergency position-indicating radiobeacon (section)

=== EPIRB activation ===
Automatic EPIRBs are water activated. Some EPIRBs also "deploy"; this means that they physically depart from their mounting bracket on the exterior of the vessel (usually by going into the water.)

For a marine EPIRB to begin transmitting a signal (or "activate") it first needs to come out of its bracket (or "deploy"). Deployment can happen either manually where someone must physically remove it from its bracket or automatically where water pressure will cause a [[hydrostatic]] release unit to separate the EPIRB from its bracket. If it does not come out of the bracket it will not activate. There is a magnet in the bracket which operates a [[reed switch|reed safety switch]] in the EPIRB. This prevents accidental activation if the unit gets wet from rain or turbulent seas.

Once deployed, EPIRBs can be activated, depending on the circumstances, either manually (crewman flicks a switch) or automatically (when water contacts the unit's "sea-switch".) All modern EPIRBs provide both methods of activation and deployment, and thus are labelled "Manual and Automatic Deployment and Activation."

==== Automatic hydrostatic release unit ====
A '''hydrostatic release unit''' is designed to deploy automatically when submerged to a prescribed depth; the pressure of the water activates a mechanism which releases the EPIRB.
[[File:Epirb hydrostatic release mechanism.jpg|thumb|EPIRB hydrostatic release mechanism]]