The Gigaset CL660 (CH version) is an analogue landline telephone that is connected directly to an analogue telephone line. The Sunrise/UPC boxes are generally IP-based routers with an integrated DECT base station for cordless telephones.

To connect the CL660 to a Sunrise or UPC box, you need an analogue telephone connection on the box. If your Sunrise/UPC box does not have an analogue telephone connection (RJ11), you will need an additional analogue telephone adapter box (ATA) to connect the telephone.

The CL660 is not designed as a cordless DECT handset for direct connection to the DECT base station of the Sunrise/UPC Box. For a DECT connection with the Sunrise Connect Box 3, a compatible DECT base station is required, e.g. the Gigaset Box 100, to which the CL660 handset can then be registered.

Summarised:
- If your Sunrise/UPC Box has an analogue telephone connection, you can connect the telephone directly.
- If not, you will need an additional analogue telephone adapter box.
- A separate DECT base station is required for a DECT connection with the Sunrise Connect Box, as the CL660 is not a stand-alone DECT handset.