Abstract: An extension repeater which interfaces between a digital service network and a local network span combines extensive diagnostic and operational functions in a single, space-efficient device. The functions include simultaneous loopback capability in both the direction of the digital service network and the local network span, signal regeneration capability in both directions, non-intrusive monitoring connections for each side of the repeater, and visual indicators of the loopback states as well as the framing type of the data received from the digital service network and the local network span. Furthermore, the extension repeater is physically sized and shaped to fit in standard wall-mount telephone equipment shelves in order to provide economical and simplified installation of the repeater at locations outside of a telephone network central switching office.