The wireless access points, cameras and other devices being mounted on our ceilings or high up on walls are connecting to our networks – but not all use standard faceplate, jack and patch-cord configurations to do so. Instead, a direct-attachment method is being used, which terminates horizontal cable with a field cable plug that plugs directly into devices.
There are two cable plug options for Category 5e, Category 6 and Category 6A twisted-pair cabling:
Crimp-on plug types require preciseness; cabling wires, contacts and plug components must line up correctly to achieve appropriate electrical performance. A crimp-on plug must be designed for each cable’s geometric differences. A PCB cable plug, on the other hand, doesn’t take cabling configuration into account. Installing a PCB cable plug is just like putting on a jack: You terminate the cable onto IDCs and place the plug housing on top. This disassociates the characteristics of the cable and plug when connecting them.
Grabbing a Category 5e crimp-on plug from the shelf and connecting it to your cable isn’t good enough if you always expect the best electrical performance possible. But it’s not a matter of finding the best cable plug available, either. A plug at either “extreme” (low performance or high performance) is bad news. Performance balance is key, and there’s a technical explanation as to why.
An inexpensive, low-functioning cable plug will cause just as many problems as the most high-performing cable plug available – they both will fail near-end crosstalk (NEXT) requirements. NEXT is a measure of unwanted signal coupling from one pair to another at the near end (closest) of the cabling.
Per standard, cable plug performance must fall within a certain range so plugs and jacks from different manufacturers can be used together and still meet NEXT requirements. This is called “interoperability,” and is the reason for industry standards. (The performance range for Category 5e plugs is wider than the performance range for Category 6 and 6A plugs.) To pass NEXT requirements, a plug’s performance must balance crosstalk interaction with connector compensation.
To visually explain what happens in these situations, we’ve created the diagram above. The vertical axis represents plug performance, with a higher-performance plug at the bottom and a lower-performance plug at the top. The horizontal axis represents the NEXT performance of the mated jack and connector.
You would expect a high-performance plug – one with little or no crosstalk – to have superior mated NEXT performance. But the diagram depicts otherwise. Why is this? When a plug is mated with a jack, the jack expects a plug that has a certain amount of crosstalk (one that falls within the plug range). Since the higher-performance plug is not within the expected plug range, the jack overcompensates. As a result, performance falls outside the requirements.
It works the same way with low-performance plugs. A low-performance plug has too much crosstalk and falls outside the plug range. When this plug is mated with the jack, it undercompensates. As a result, performance falls outside the requirements.
The moral of the story: Cable plugs matter. They can’t be too “bad,” but they also can’t be too “good.” Otherwise, their performance will fall outside the acceptable plug range and the mated near-end crosstalk performance will cause issues with reliable performance of your data cabling channel.
Belden has been working on a Direct Connect field-mountable plug, which is a PCB-type plug that efficiently connects IP devices to the LAN with excellent performance.
To learn more about why cable plugs matter, sign up to attend our free webinar on Jan. 10, 2017. We’ll discuss this topic in more detail, along with other things you can do to prepare your LAN for the future.
Ron joined Belden in 2016 to help define the roadmap of technology and applications in the enterprise. Prior to this, he developed cables and connectivity for Panduit and Andrew Corp. Ron Tellas is a SME in RF design and Electromagnetic Propagation and has BSEE from Purdue University, a MSEE from IIT, and a MBA from Purdue University.