Siemens HiPath 3000 Operating Instruction page 16

Putting the handset into service
3. Secure the handset with the attachment clip to the belt. To do this,
To remove the handset, press the opener on the attachment clip and slide
the handset from the pin.
16
open the brackets by squeezing the free end and attach it to the belt.
While you are wearing the handset on the belt you will be able to
read the display without having to remove the handset, see
 page 135.