The most commonly used cabling in the TDM ring is: Category 5 Ethernet cables.

Use industry standard, Category 5, 4 pair, UTP network cables when creating the ring. This cabling will work with the older through-hole and the newer surface-mount TDM cards.

It is possible to extend the ring length beyond that possible with Category 5 by using Category 6 Ethernet cables. Use Belden media twist 1872A (or equivalent*)

*At the time of this writing, the Category 6 standard is not official. Specifications vary from one manufacturer to another. The specifications for the cabling tested by ASTi is available at http://bwcecom.belden.com under "The Belden Catalog Technical Info" and search using the keywords "Media Twist".