Hi,
The "devices that are plugged into a socket" is probably the "Powerline Connection Kit".
The TV Box will need about 8Mbps for normal TV, and even watching full HD content etc. you will hardly have issues with speed. Swisscom seems to sell a model doing 100Mbps, in any IT shop you will find more models/brands (Devolo is one of the historical brands in this market) going up to 1Gbps (and more in theory).
You also have a wireless connection kit sold by Swisscom going over wifi and of course buying a longer cable (up to 100m).