There are several constraints which determine whether ADSL can be provided “on top of” a particular telephone line.

First the telephone exchange must be equipped with a DSLAM provided by the carrier or Service Provider.
Secondly the particular customer location must be within approximately 3.5km of the telephone exchange.
Thirdly there must be no impediments to the service (pair-gain, loading coils, ..) or interfering services on the line.
While this sounds complicated, Greenbay will handle these checks for customers so that it is a fast and simple process to “service qualify” the line. The national rollout of ADSL by a number of carriers means that the majority of users in urban areas in metropolitan and provincial cities will have access to ADSL.