You need two phone lines as there must be a separate ADSL device at the DSLAM.
Even with that you would need a device to load blanace the two links or something similar depending on your use of the two connections.
Können Sie zwei ADSL-Anschlüsse an einer Telefonleitung haben? Oder erfordern zwei Breitbandverbindungen laut IT-Recht zwei separate Telefonleitungen und BT-Master-Steckdosen?
You need two phone lines as there must be a separate ADSL device at the DSLAM.
Even with that you would need a device to load blanace the two links or something similar depending on your use of the two connections.