AASTRA 4425 IP Vision for BusinessPhone User Guide - Manual (Page 136)

Installation
BusinessPhone – Dialog 4425 IP Vision 136
Install cables
You can put the cable to the handset in the notch underneath the
telephone. The cable to the exchange has to be plugged in LINE
and the handset cable has to be plugged in HANDSET.
Note: The installation of the 24 V power adapter is optional.
If no external power supply has been installed, the
telephone will rely on the LAN power supply.
Change cables
To remove a cable, use a screwdriver to unlock the stop.
Handset cable to the left Handset cable to the right