ACR Electronics RLB-38 Product Support Manual page 12

Category I beacons-Automatic deployment and activation
If the vessel sinks, the HydroFix™ HRU frees the beacon from the bracket,
allowing it to float to the surface. Built-in sensors detect that the beacon is
no longer in its bracket and when continuity is created by water between
two of the top cap screws, an activation circuit is completed.
NOTE: Transmission of the 121.5 MHz and 406 MHz signals will not occur
until 100 seconds after activation.
HRU releases the rod
separating the front and
back cover of bracket at a
depth between 4-13 feet.
Y1-03-0250 Rev. C
Ejector Spring launches EPIRB
from the bracket allowing it to
float freely to the water surface.
11