Aastra M401 User Manual page 21

You can transfer the call to the person requested by pressing
then
Dialing the extension number
Hang up when he/she answers
4.3 PICKING UP A CALL WITHIN YOUR EXTENSION GROUP
You are a member of an extension group (groups are defined by your telecom administrator).
This means that group members can pick up calls ringing on the extension of other members.
If you hear a colleague's extension ringing when he/she is absent, you can pick up the call
from your own extension.
Picking up a call ringing on another extension in your group
On your keypad:
Pick up the handset
Press the following keys consecutively
You are connected to your colleague's call.
At the end of your conversation, replace the handset.
Call pickup
R
EXTENSION NUMBER
0
20
1