Technical Reference: T1 Cable

When T1 was first introduced Western Electric provided ABAM 600 to support it.  This cable was a 22 gauge, 100 ohm insulated, twisted pair.  ABAM cable is no longer available, but you can easily find cable that meets the technical requirements. Nearly all major manufacturers of wire and cable supply a version of T1 cable.  In general, T1 cable is two twisted pairs of 22 AWG, 100 ohm wire with the added characteristic that each pair is individually shielded.  Both of the shielded pairs are enclosed in a single PVC jacket.

If you cannot obtain T1 specific cable, then use two runs of CAT 5.  Use one CAT5 cable for the Transmit (Tx) signal and one CAT5 cable for the Receive (Rx) signal.  It is necessary for the Tx and Rx signals to be in separate sheaths to prevent cross talk interference  

Specifications for the original ABAM manufactured by Western Electric in the early 1970's:

Maximum cable length between CSU and CPE


655 feet


455 feet

Cable Pin Outs:

8 -pin modular connector wired as a RJ-48-C block.

Color Code:

There are two common color codes in use.  The more common of the two is called 568-B.  The diagrams below show the 568-B color code.

568 B: 


568 A:  

 With this format pairs 2 and 3 (Orange and Green) are reversed, making it functionally incompatible with the e568-B format.


. . . go back to the AHK home page

Copyright   2003 by AHK & Associates, Inc

Last updated: Sunday, April 20, 2003