On Sat, 19 Jan 2008 17:25:39 -0800 (PST), "
wrote:


There is one mysterious feature. On the top of the pressure casing
there is a small resin colored plug.

Obviously :-) a porous plug which equalizes pressure when dry and does
not do so when wet.

It is visible from the outside
of the case through a hole in the label. I presume this keeps the
device from exploding if you take it up into space or something. On
the other hand it could be the little bit that dissolves every two
years so you have to replace it... Or, perhaps, they use the hole to
fill the chamber with inert gas... In any case, if the bung were out
the device would not operate. I suppose it is worth looking to make
sure it is there periodically, particularly if the release has been in
an airplane.

-- Tom.