9.2.2. Activation via menu 
The menu items “MOBILE HFA LOGON/LOGOFF” for mobile HFA are located
in the service menu. Activate the service menu at the visited phone and
step forward/backward with the buttons “<“ and “>” until
the menu items for mobile HFA logon/logoff are reached.
The mobile HFA feature can also be reached with service menu and digit
“8’”(mobile HFA logon) and digit “9” (mobile HFA logoff).
After confirming logon the user is asked to enter home number and
PIN like above.
After confirming an action the behavior is the same like DAR activation.