Accenta 6?

I have taken over house with an Accenta 6 which has not been used for several months - the fuse was withdrawn by the control box.
On pushing in the fuse, a fire alarm beeped and the internal alarm sounded followed by the external sounder.
I tried putting in the code & reset, but the only way to stop the sounders was to withdraw the fuse.
Help!
Where do I go from here?