PAIRING STP PRODUCTS
Q: I am designing the electrical system for a local police facility, to provide an IEEE 802.3 10Base-T network. The client requires shielded Category 5 cable; however, I cannot seem to pair up a shielded Category 5 cable with an appropriate Category 5 RJ-45 jack. According to an article in Cabling Installation & Maintenance, pairing products from the "wrong" manufacturers can cause problems (see "Screened 100-ohm cabling gains acceptance in high-speed networks," April 1996, page 37). Most of the runs are well under 150 feet; therefore 26 AWG is not a problem. Can you recommend any products that will suffice?
Steve Dittman
Dittman Associates
Pismo Beach, CA
A: My answer is similar to the caution that Ned Sigmon of AMP Inc. (Harrisburg, PA) wrote on page 46 of the article, "... the user or installer should verify that the connector manufacturer has complied with the proposed requirements..."; but with a slight twist. Because you have not seen the requirements in the proposed Telecommunications Industry Association Telecommunications Systems Bulletin (TSB) on screened twisted-pair cabling, and most of the manufacturers of 100-ohm shielded twisted-pair (STP) cabling are represented on the task group drafting the requirements, why not shift the compliance responsibility to the manufacturers?
I would suggest that you have your cabling supplier contact the manufacturers they represent (or get the list from your supplier). Contact the manufacturers directly and request answers (in writing) to the following questions:
- Do you provide an end-to-end cabling solution for 100-ohm STP cabling?
- Are your 100-ohm STP cabling system components compliant with the draft TSB?
- After the TSB is published, if your 100-ohm shielded cabling system components are not compliant, what relief do you intend to offer the end user?
Until the TSB is published and all manufacturers begin to ship compliant products, I would recommend that you order all 100-ohm STP cabling system components from one manufacturer.
