Alarm on GDX Intercom Handset

Hi everyone,

Hoping you can help me figure something out.

I've recently moved bought my first flat and the previous owners were a couple that were all but deaf. As a means to cope with this, the intercom system they had installed was rigged to have the lights in the flat flash and there is also an alarm box that will give off a (somewhat ironically) deafening sound.

We've been able to remove the system that flashes the lights, but the alarm box is proving a bit trickier as it doesnt need simply removing, but replacing with a quieter alarm so that we can still tell when there is someone looking to buzz the intercom to our flat.

With the complete ignorance of someone who has limited knowledge of circuits, I imagined all I'd need to do is replace the alarm box with another and it would work. In the current alarm box, there's only two wires and so there shouldnt be any complicated wiring.

However, when I attempted to replace, the new alarm chimed constantly when connected, even when nobody was buzzing to the flat.

The attached pictures:
Pic 1 & 2: The old alarm which I believe is a Kinetic Twin Piezo Sound Bomb
Pic 3: The new door chime, a Byron 761
Pic 4: GDX Intercom Handset

Is anyone able to advise what my problem was?

Does the handset not ring when the sound bomb is removed ? As I normally fit sound bombs on intercoms when they are a bit deaf ...the handset should still have a normal ring ....

Thanks a lot for the help! For some reason, I imagined that the handset didnt have it's own ringer, which is why one needed to be connected and so I didnt even attempt to see what happened without one attached.

After the deafening sound of the last ringer, this one seemed a little quiet, but we've adjusted back now and it's much better. Thanks for the help, you've saved our sanity and eardrums

I can't quite see from the photo, and it's not the same circuit board as the one at IntercomsRUs, but behind the cable is there a small rotary control? That may adjust the sounder volume.