If your handset's line belongs to a Mulap group (Multiple Line Application), then you can 

answer calls for the group (press the Talk key in group calls)

make external telephone calls under the group phone number (the group phone number is stored in the called party's caller list, for example )

activate and deactivate the group call function for your handset's line

forward the lines of the Mulap group to internal or external destinations

Activating/deactivating group calls

Press the Talk key. 

Call the system menu. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Press the On-hook key to end the process. 

Forwarding a Mulap line

You can immediately forward internal and/or external calls to your lines to different internal or external telephones (destinations) (external destinations are also possible if the system is configured accordingly). 

If you activate call forwarding for a line, this shall apply to all line keys of your group for this line. 

Forwarding on 

Press the Talk key. 

Call the system menu. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Enter a line number. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Enter the destination number. 

Save the settings. 

Press the On-hook key to end the process. 

Forwarding off 

Press the Talk key. 

Call the system menu. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Select and confirm the menu item. 

Enter a line number. 

Press the On-hook key to end the process.