- If 4 handsets are already registered, one of the handsets would display ?Handset 4? * If your base is not fully registered, follow the steps below to pair (or register) the handset with the base station * If you are using a non-Philips brand handset or base station, refer to the user manual of that handset or base station Note: Registration using a non-Philips brand handset or base station may not be possible.