CDJ

You said in first post that the Bell activates when you removed the power from the bellbox. - So it seems to be self activating ok. That then suggests the trigger from the panel is not working right, either bad connection/short between trigger and -12v (for negative tamper) or perhaps bell is set for neg trigger when panel is positive (or vice versa - though perhaps more likely to have a constantly wailing bellbox if this was the case, I've never tried this, either accidently or on purpose). You could test the trigger in the panel with a multi-meter to check its changing/sending correct signal when bell activated, however thats assuming that you installed the panel and are confident opening it up and using multimeter. CDJ

Not certain on the Veritas but other panels (including Texecom Premier series) have an option were only Internal bells will sound if its an entry alarm (only sensors on entry route activated) rather than a full alarm hope that helps