Ericsson DIALOG 4220 - Manual (Page 66)

Other Useful Features
Dialog 4220 Lite/Dialog 4222 Office 66
Data communication
Your Phone can be used together with a PC as an integrated voice
and data terminal. Contact your System Administrator if you require
this Function.
Additional directory number
You can be assigned (programmed by your system administrator)
one or more Additional Directory Numbers (lines) on free function
keys.
To answer, make calls and use functions on the additional directory
lines, use the same procedure as for the Triple Access Lines if
nothing else is stated. However, you have to press the additional
Line key after lifting the handset.
Example:
To make a call on an additional directory line:
u
Lift the handset.
Additional line
Ô
Press.
Note: Function key preprogrammed by your system
administrator. z
Dial the extension number.