Intercom handset identification help

[Jfogwill]

Hi,
My girlfriend has moved into a flat and she can talk down to the front door but she can't hear anything back, the door unlock button works fine.
We asked neighbors if there handsets were working and they said all fine.

I thought it might be a faulty speaker and that I could just replace the handset with a like for like but I can't find a match anywhere. The outside says comlit but when I opened it up the circuit board has a sticker someone has written gdx phone 3 on.

I've found the case but the internals don't match what we have and I can't find the circuit board on anything not even the gdx3 pictures I've found match.
Any help at all would be appreciated.

Jack

 

[sparkymarka]

Give intercoms r us a ring ....looking at this it’s a modified comelit for pac/blick who then became stanley ....where the GDX comes into play