User's Manual

Page 9
3.2 Float-free enclosure
If you purchased the automatically activated version (‘a’ suffix), also known as the
“float-free” version, then your EPIRB is supplied in a plastic enclosure (see section 9).
This is much more than just a protective housing; it contains a spring-loaded lever
which automatically pushes the enclosure lid off and releases the EPIRB if your vessel
sinks. This automatic ejection is controlled by a device called a Hydrostatic Release
Unit (HRU). If the enclosure is sinking then before it reaches 4 metres (13 feet) depth
the HRU cuts a plastic rod that retains the lever; this ejects the lid and releases the
EPIRB which floats to the surface and switches on automatically, as shown below:
1. As the vessel sinks, the enclosure fills with water. The HRU contains a
blade which is released due to water pressure acting on a diaphragm.
Before it reaches a depth of 4 metres, the HRU will operate and cut the
plastic rod, releasing the coil spring.
2. The spring pushes the EPIRB and the enclosure lid outwards. As the lid
pivots off it disengages from the moulding lip that helped hold it in place.
The lid is weighted so it rolls over and falls away.
3. As the EPIRB floats away, it moves out of range of the magnet. Once
away from the magnet its sea switch becomes armed.
4. The sea switch activates. The EPIRB then floats on the water surface
with its strobe light flashing. After 50 seconds it makes its first distress
transmission.
If you need to activate your EPIRB manually, it can be freed from the enclosure after
pulling out the R-shaped retaining pin and removing the lid.