How to register the Gigaset SL400H Additional Handset:
1 On the phone base station of your SL400A (the black unit that is connected to the phone socket), press and hold the paging button for 5 seconds until the base beeps. The base is now in registration mode.
The next steps must be finished within 60 seconds.
2 On the handset you want to register (it may show "No Base" on the screen), please press the right side of the navigation button, the handset will enter MENU.
3 Using the navigation button, select the spanner icon ("Settings") and confirm by pressing "OK"
4 Scroll down until the option for "Registration" has been highlighted and confirm your selection by pressing "OK".
5 Select "Register Handset" by pressing "OK", and the message 'Searching for a base that is in registration mode' will appear. If prompted to enter the system PIN (the default is 0000) do so to complete the registration.
Registration can take up to 60 seconds, and will be confirmed with on-screen message as pictured below.