9427 alarm?

hi
last year while we was away we had aterrible thunder storm that broke me alram system recently i have changed the fuse and it has come back on the problem is now we dont know how to use it it was some years ago that we had this installed and we cannot remeber who installed it for us the only code that works is 1234 but apart from that nothin we thought that by keyn in this code we could put our alarm on and leave the house but after 20 sec the alram goes off please can you help us sortin the alarm out