Sprint International Communications Corporation

Theodore S Holdahl

Carl J Bushue

A method and apparatus for providing troubleshooting capability in a four wire telephone line employing a V.32-type or other unbalanced modem in a local communication link at one or both ends of the telephone line for a data network. Each modem has its own transmitter and receiver. An activatable but normally inhibited analog loopback is installed externally of the modem within the local link with which the modem is associated, with no loopback connection between the transmitter and the receiver within the modem itself. The external loopback is activated while the modem is induced to transmit a call connection signal, so that by virtue of the external loopback the signal is fed back to the receiver of the same modem to permit testing of the operativeness of the modem and the related portion of the link. The external loopback may be activated from terminal equipment on the local link with which the modem is associated, or may be activated from a point of the network remote from the local link.

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Lake Quivira, KS, United States of America

Theodore S Holdahl