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I am not an expert, so what follows is just my humble opinion, and most certainly not authorititive.
When you say “I cannot have access to Internet in any of the rooms” I assume you mean WiFi access,
because you could get wired ethernet access to the Internet using ethernet cables in the multimedia
sockets in the cellar (for the Internet Box) and in the rooms (for your desktop PC’s, TV-Box, etc.).
To get WiFi access to the Internet in the rooms I think you need a “WiFi Access Point” (NOT a "WiFi
Repeater"!) with at least one RJ45 ethernet port. You would place the “WiFi Access Point” somewhere
central in your apartment or house, so that its WiFi signals can reach all the rooms. Then you need
two ethernet cables: one leading from the “WiFi Access Point” to the nearest multimedia socket, and
one in the cellar leading from the corresponding multimedia socket in the cellar to the Internet Box.
Searching www.digitec.ch for “WiFi Access Point” reveals a selection of devices for around CHF 100,
but it must have at least 1 RJ45 ethernet port, and it must also function in such a way that the
RJ45 ethernet port is designed to be connected to a router, for the purpose of providing WiFi access
on behalf of that router (Sunrise Internet Box). It should also provide the WiFi flavours you want.
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