1988 300SE Alarm Stays On

[bevanet]

Hi, The alarm went on when one of my kids opened the back door before I did. Now I can't get it to turn off. I've tryed locking and unlocking the driver's door several times, starting and driving, letting it stay on. I've tried disconnecting the battery for a long time (it still comes on every so often and beeps for a while after I connect the battery). I finally removed fuzes until it turned off, but the fuse also controls other things that I need. When I insert the fuse it starts beeping again. Is there anyway to reset it? or is the central locking system broken?