1992 Rodeo alarm problem

If anyone can help, I'd sure appreciate it. Just replaced the battery in my 1992 Rodeo. As soon as I connected the terminals, I heard a
short whoop from the alarm system. Then when I opened the door, the alarm went off. I had forgotten I even had an alarm. For the last 5 years I've been driving it with no alarm problems at all. The red alarm 'armed' light has never been on at all for those 5 years. Now, the armed light starts flashing as soon as I connect the battery. How can I make the alarm go away? My Rodeo doesn't have a remote. It has manual locks that I just use a regular key for. I tried connecting the battery with all the doors locked and then used the key to unlock and open the door - the alarm starts howling. Any suggestions are appreciated on how to either disarm the alarm or how to permanently disconnect it. Thanks.
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