Link conundrum – DB15->RJ45-Possible?

I have a Newbridge Mainstreet 2701 DTU (DSL) with a DB15 device port. I could save over $500 for many clients if I can connect this port to an RJ45 port of a Cisco 827 router. The manuals show many other types of possible conversions but I feel that this connection can be made. The link speed is 128kbps. can anyone help? Kizito in Uganda.