AASTRA 4225 for MX-ONE Telephony Switch - Manual (Page 112)

Settings
Dialog 4223 Professional/Dialog 4225 Vision 112
Activate or deactivate a stored melody
A stored melody has to be activated in melody mode to be heard when
you get an incoming call.
To activate (in melody mode):
Line
Ô
Press the key for the requested type of call (Line 1 or Line 2 or
Inquiry).
The corresponding key lamp is switched on:
Line 1 key = Internal calls
Line 2 key = External calls
Inquiry key = Callback calls
Note: If you want to return to an ordinary ring signal but keep
the melody stored, press again the key for the requested type of
call. When the key lamp is off, the stored melody is deactivated.
Exit Press to exit melody mode (see display).