HDSL is a powerful, cost-effective, T1-based transport technology that
leverages existing copper infrastructure and is, therefore, of great interest to
both subscribers and service providers. It uses central office (CO) units at the
carrier's office and remote units at the customer site and may, depending
upon distance, require HDSL repeaters over the length of the copper span.
The power needed to operate the repeaters and remote equipment is provided
over the span itself, and must be handled safely for the protection of users
and telephone company craftspersons....