AASTRA 4220 Lite for BusinessPhone User Guide EN - Manual (Page 84)

Installation
BusinessPhone – Dialog 4220 Lite / Dialog 3210 84
Installation
Dialog 4220 Lite
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.
Change cables
Use a screwdriver to unlock the stop.