Yes, DSL requires a DSL modem as well as an Ethernet port to your PC or laptop.
You will need to have an ethernet card in order to use dsl or cable internet with your computer.
dsl cable router
A DSL modem is connected to an Ethernet port (looks like a over-sized phone jack)
PS3 can only get an online connection with DSL or Cable WiFi or ethernet
Connecting Internet throgh DSL Modem by using Ethernet port is the most rreliable & trusted way to get the best performance on a computer. Using DSL through USB makes system slow & doesn't provide the best of the available bandwidth. Moreover Through Ethernet DSL Modem can enable access to multiple computers by using a network switch.
In order to connect to the DSL modem we need to have an operational Ethernet port on the computer. That is what the user guide is referring to. Earlier data connections (dial up) on phone line modems did not require an Ethernet port. All DSL modems now transfer data to computer through an Ethernet port (wired or wireless).
Broadband cable and DSL WiFi or ethernet connections
You can connect your Xbox by wireless or wired (ethernet).
You don't - you'll need an Ethernet card for your computer. A regular voice/fax modem is different than a high-speed/network connection, so you need a different 'card' (with a socket that will match your cable). If you can't find a socket that your Ethernet cable fits, then you don't have an Ethernet card installed!
you need an ethernet cable
The DSl wireless router tranfers information to your computer via the ethernet cord. You can only use a phone lline for dial-up.