omnicron 90005 problems after power fail

["mojohotmail" <mojo7676@xxxxxxxxxxx>]

Anyone happen to know how to resolve the following problem? Omnicron 90005
domestic alarm box - fitted for a while (it's old but seems/ed to work 100%)
has stopped working altogether. A fuse in the main consumer unit blew so i
guess the box was running off the battery (?) for a couple of days and
today, the siren/bell started wailing. The siren/bell stopped after a little
while but now there box appears to be completely dead - no lights, no
functionality whatsoever. I've not tried opening the box up or anything in
case i make things worse. Any pointers to get the thing going again? Does it
need to be somehow reset or does the battery need changing? Now that there
is electricity going to the thing, i'd have at least thought it would have
lit up etc. Complete novice with these matters, in case it's not obvious.
tia. mojo.