In the Hybird 120 Gigaset Edition go to "Assistants" - "PBX" and click on "New": --> add a new SIP Provider
Give the Line an unique name, insert the Registration user name and Password.
Just add the telephone numbers for this SIP trunk in the "Advanced Settings"
Here you can define how the outgoing lines have to look like (e.g. Clip no Screening)
Please choose here the below settings when you use the CLIP No Screening.