Field Terminated Series: Part 2
Field terminating 8position modular plugs onto cables and within cabling systems.
In the last iteration of CTD, we began to discuss the interest and drivers behind terminating the device end of 4 pair horizontal cabling with 8 position modular plugs, or a Modular Plug Terminated Link (MPTL).
To build what we discussed in the last publication, what follows is an attempt to pose and provide answers to some increasingly frequent questions. Before we get started, I would like to thank Cindy Montstream for her expertise and input on TIA and other standards bodies we consider. I’d also like to thank Carol Oliver for work and input on BICSI’s 005 (ESS) and 007 (Intelligent Building) standards. As always, the DCD Training & Technology department is an excellent resource for standards and best practices.
Question #1 Are field terminated modular plugs allowed in the TIA/EIA 568C and related standards
? The use of field terminating modular plugs has not been recognized in the past by the TIA standards. TIA has recognized direct connections in both the ANSI/TIA-862 standard for Intelligent Buildings and ANSI/TIA-942 standard for Data Centers. The ANSI/BICSI 005 standard also recognizes direct connection, similar to the TIA-862 standard. (Note: TIA standards define generic cabling topologies, design, distances and outlet configurations as well as specifics for these locations. BICSI standards provide recommended best practices and recommendations for proprietary systems not addressed in the TIA standards). The next revision of the copper component and cabling standard, TIA-568.2-D, is set to include cabling framework for direct connection using a field terminated modular plug, which will be referred to as a Modular Plug Terminated Link (MPTL).
Question #2 What does “used within the cabling framework allowed by the TIA standards” mean?
Plug terminated components are recognized and allowed within the current permanent link and channel definitions of the 568C standard. Plugs terminated onto horizontal cables that plug into a modular consolidation point or plugs that are on cables coming from the back of a panel to plug into the front of another panel are allowed because they comply with the channel & link guidelines and (equally important) they can be tested as part of the final installed link or channel. Patch cords built in the field are also allowed because they can be tested to the patch cord component specification.
There are situations when terminating one end of the horizontal cable and plugging directly into a device might make sense or be the most feasible option. That’s why TIA is including an Annex in the new revision of the TIA-568.2 standard (ANSI/TIA-568.2-D) for MPTL. As stated in the standard,
“In certain limited cases there may be a need to terminate horizontal cables to a plug that is directly plugged into a device. This will sometimes be done to service a security camera, a radio enabled wireless access device, or another device which is not often moved or rearranged. This annex provides guidance to assure the proper functioning of such a cabling arrangement.”
Question #3 Can field terminated modular plugs be used in place of a TO jack and patch cord at the end of a 568C compliant channel?
The answer to this question has been NO
. That is changing with the inclusion of the MPTL (modular plug terminated link) for limited use cases in the new revision of ANSI/TIA-568.2-D that is currently being worked on in TIA. The current draft of the standard requires modular plug terminated links to comply with the permanent link transmission requirements within the standard.
The current proposed test setup is shown below.
Question #4 Can channels with field terminated modular plugs, used in place of an EO jack and patch cord at the end of a channel, pass the TIA 568 channel test? Yes, however the Jack EO is considered a permanent part of a buildings cabling infrastructure, which supports the mission of the standard to provide cabling with a life expectancy of at least 10 years. When channel tests are conducted, the field tester does not include measurements associated with the plug that is inserted into the tester. Therefore, a channel test does not include all of the effects of the end plug so issues with the plug termination may not be visible.
Question #5 What can today’s field testing identify regarding field terminated modular plugs used in place of a TO jack and patch cord at the end of a channel? A channel test will validate correct wire map and continuity. Other performance measurements will not include any contributions of the end plug.
There are field testers that are including MPTL testing in either their software updates, or in their new devices. For example, With the new Fluke DSX-8000 CableAnalyzer, and now with updated software on the DSX-5000 CableAnalyzer, it is possible to test a link when the far end of the cable has been terminated with a RJ45 plug, known as a Modular Plug Terminated Link test, or MPTL.
They do not imply this testing will be accepted by cabling vendors testing this to obtain a warranty, and suggest you contact your cabling vendor regarding how this test is viewed compared to their typical test requirements.
To learn more about Fluke’s MPTL, visit this link: http://www.flukenetworks.com/knowledge-base/dsx-cableanalyzer-series/modular-plug-terminated-link-mptl-test-limits-dsx-5000-and
Other tester manufactures claim to be able to test a link when the far end of the cable has been terminated with a RJ45 plug. Some call it “modified direct attach” although some expect that term will change. I did not find any explanations so far that were as detailed as Flukes.
Question #6 Can field terminated modular plugs be used in place of an EO jack and patch cord at the end of a Device or System specific cabled channel?
Because system or device cabling is only intended to support the life of that system or device, the answer appears to be YES, or at least there is not a definitive NO. The intent of the TIA standards is to provide guidelines for using a field terminated modular plug for limited cases with devices like cameras, sensors, etc., when an outlet and patch cord may be difficult to use. It is not the intent to generally recommend using a field terminated cord in the place of an EO (equipment outlet) jack and patch cord.
Question #7 Can field terminated modular plugs be used to produce Direct Attach cabling?
Field terminated modular plugs can be used for direct attach cabling or point-to-point cabling when needing to plug directly into a device for limited use cases as previously mentioned. One end of the horizontal is terminated with the modular plug and the other is punched down on an interconnect device (patch panel, etc.). TIA does not specify, nor recommend a field terminated plug on both ends of the horizontal cable. There are several reasons field terminated plugs have not been recognized in the past. These include, but are not limited to the fact that is that it is hard to achieve performance requirements and have consistent performance with field termination. One addition consideration would be the physical compatibility since a PCB version of a field term plug with jack type wire termination is typically larger than a booted or non booted factory terminated plug and the larger size would need to be accommodated.
Question #8 What changes are coming?
As stated earlier, TIA is working towards developing an approach that would support devices that are considered permanently located by defining performance and testing requirements for a field terminated plug used for point-to-point connection. Watch for updates on the TIA-568.2-D standard.
Question #9 What approaches should you consider?
The TIA and ISO standards are voluntary, not regulatory guidelines, however they provide well-vetted blueprints for cabling infrastructure. The recommendations they provide were designed so that components from any manufacturer will meet minimum guidelines and will perform when used together. There are multiple industry resources, including Legrand that can assist in your research and evaluations of the best choice for your specific application.
Finally, Stay current
with the standards work that is going on. There are expected changes and expansion to cabling approaches and these changes will continue to be introduced over the coming months. Also, check out the Legrand University
for standards updates, found under Ortronics or Data Communications.