At&t Bell Laboratories

Bell Telephone Laboratories

Kenneth B Parks

Harold Wayne Friesen

Wendell G Nutt

Luc W Adriaenssens

A balanced mode transmission system (20) for use in a local area network includes at least one twisted pair of insulated metallic conductors (27--27) which at its end is connected through a transformer to a transmitting computer and to a receiving computer (48). Each pair of conductors adjacent to the transmitting end and optionally adjacent to the receiving end is provided with a longitudinal choke (56,57). Also, a longitudinally extending metallic wire (60) is included in the system and is connected possibly through a resistor to ground at each end. The combination of the longitudinal choke at least adjacent to the transmitting end and the longitudinally extending metallic wire is superbly effective in suppressing electromagnetic interference notwithstanding the absence of shielding.

Communications transmission system including facilities for suppressing

Multipair cable testing apparatus for detecting transpositions and reversals in the cable pairs includes master unit (100) located at one end of the cable and remote unit (200) located at the other end. Master unit (100) comprises: pair address generator (120) for automatically and sequentially stepping through a grouping of pairs simultaneously terminated by master unit (100); sequencer (110) to sequentially connect, during each testing step, a pair under test to voltage measurement means (150) and then to resistance measurement means (160); indicator means (170) to display the results of the two measurements; and communicating means (175) to transmit the terminal address of the pair under test to remote unit (200). Remote unit (200) comprises: decoder means (210) for receiving the address information of the pair under test; means (220) for terminating the grouping of pairs at predetermined addresses and placing a voltage on all pairs located at the predetermined address except for the pair having the preselected address; and polarity-sensitive resistance means (226,227) connected across each pair and oriented to provide low resistance for a reversal. Indicator means (170) signals a transposition whenever voltage means (150) measures a voltage greater than a predetermined threshold and signals a reversal whenever resistance means (160) measures a resistance less than a predetermined level. Cross-connect apparatus (300) effects detection of transpositions between different pair groupings, and extends automated testing capability to any number of groups.

Growing community of inventors

Lilburn, GA, United States of America

Kenneth B Parks