alarm won't shut off
 

I have a 1988 300E 4 door 6 cylinder ,My battery went dead and I replaced it with anew one now I have aproblem with my factory installed alarm will not shut off,reset it by disconnecting the battery several times and it seems like the problem won't go away horn is being activited and headlights flashing, is there anyway I can disarm or reset this? or is there any code and where can I enter a code if there's any? please help...