http://www.infinititelecommunications.com.au/phone-systems/phone-system-handsets/alcatel-phone-handsets/alcatel-4039-handset.html
Do not disturb on the Alcatel 4039 Phone Handset - To look at the 4039 handset is almost identical to the 4029 executive phone except that it has 10 soft keys not 6. This means you can see more on the screen without having to scroll down. It is compulsory to have at least one 4039 on an Alcatel phone system for programming purposes but that is all you really need.
http://www.infinititelecommunications.com.au/phone-systems/phone-system-handsets/alcatel-phone-handsets/alcatel-4039-handset.html