ADT alarm bell not ringing?

He'll all hoping for a wee bit of help regarding my outside bell box.

We moved into our home and fitted is a galaksy alarm and ADT outside box,problem,when we trigger the alarm the outside box remains silent but the inside siren activates.

What I would like to know is how to switch the outside box on so when the alarm is activated it rings,i'am assuming it's been muted by pressing a button on the keypad but i dont know what buttons are pressed.

Many thanks in advance tj.