What i would do is buy some RJ11 to RJ11 cable and use a cheap usb modem like the speedtouch 330(Most people have millions of these as it all ISPs used to ship).
What to do:
*Cut cable in half
*Strip about 1inch of each end
*try 3-3 + 4-4(just twist the wires or use crocodile clips if you have any)
*try 3-4 + 4-3
Testing speed and stability on each test.
This would be a very good,safe and cheap experiment to try(i would but my HTTP and SMTP servers have to stay up otherwise i will have sore ears tommorow LOL)
****Telephone lines can only provide a small shock and you can relax your muscles and let go(I would still unplug it from the wall socket first LOL)
EDIT: I personally use 2x2(2 sets of two twisted wires) from a CAT6 cable in a 3-3 + 4-4 config.
James Barlow