Cables > CAT5e

Straight-pinned cable has the most common type of pinning. The send and receive pairs are wired straight-through on either end of the cable.

Crossover cable is generally used for peer-to-peer connections. The send and receive pairs are crossed between Connector A to Connector B on either end of the cable.

Solid-conductor cable is designed for backbone and horizontal cable runs. Use it for runs between two wiring closets or from the wiring closet to a wallplate. Solid cable shouldn’t be bent, flexed, or twisted repeatedly. Its attenuation is lower than that of stranded-conductor cable.

Stranded cable is for use in shorter runs between network interface cards (NICs) and wallplates or between concentrators and patch panels, hubs, and other rackmounted equipment. Stranded-conductor cable is much more flexible than solid-core cable. However, attenuation is higher in stranded-conductor cable, so the total length of stranded cable in your system should be kept to a minimum to reduce signal degradation.

One of the most important cable measurements is Near-End Crosstalk (NEXT). It’s signal interference from one pair that adversely affects another pair on the same end.

Not only can crosstalk occur between adjacent wire pairs (“pair-to-pair NEXT“), but all other pairs in a UTP cable can also contribute their own levels of both near-end and far-end crosstalk, multiplying the adverse effects of this interference onto a transmitting or receiving wire pair.

Because such compounded levels of interference can prove crippling in high-speed networks, some cable manufacturers have begun listing Power Sum NEXT (PS-NEXT), FEXT, ELFEXT, and PS-ELFEXT ratings for their CAT5e and CAT6 cables. Here are explanations of the different types of measurements:

NEXT measures an unwanted signal transmitted from one pair to another on the near end.

PS-NEXT (Power Sum crosstalk) is a more rigorous crosstalk measurement that includes the total sum of all interference that can possibly occur between one pair and all the adjacent pairs in the same cable sheath. It measures the unwanted signals from multiple pairs at the near end onto another pair at the near end.

FEXT (Far-End crosstalk) measures an unwanted signal from a pair transmitting on the near end onto a pair at the far end. This measurement takes full-duplex operation into account where signals are generated simultaneously on both ends.

ELFEXT (Equal-Level Far-End Crosstalk) measures the FEXT in relation to the received signal level measured on that same pair. It basically measures interference without the effects of attenuation—the equal level.

PS-ELFEXT (Power Sum Equal-Level Far-End Crosstalk), an increasingly common measurement, measures the total sum of all intereference from pairs on the far end to a pair on the near end without the effects of attenuation.

The news on bandwidth
The need for increased bandwidth never ceases—the more you have, the more you need. Applications keep getting more complex, and files keep getting bulkier. It won’t be long before you need to increase the speed of your network.

Don’t worry. Black Box experts are ready 24 hours a day to answer your questions. When you click on “Talk to a Tech,” you’ll be talking to a trained expert in seconds. If you need help installing a network, or adding an additional drop, contact us.

Because unshielded twisted-pair UTP cable is by far the most common networking cable, let’s take a brief look at where UTP is headed.

The limits of Category 5
Category 5 (CAT5) cabling is good, solid cable for 100-Mbps LANs. The Category 5 standard has been around since 1991, so it’s well established. You’ll find existing Category 5 installations everywhere. What can Category 5 cable do, and what can’t it do?

If you still have a lot of 10-Mbps equipment, CAT5 cabling will serve your needs. It also handles 100-Mbps Fast Ethernet transmissions very well.

But if you’re running up against the performance limits of a 100-Mbps network, you’ll probably want to upgrade at least parts of your system fairly soon to Category 5e (CAT5e) or higher.

Category 5e: the improved Category 5
Category 5e, also known as Enhanced Category 5, or CAT5e, was ratified in 1999. It’s an incremental improvement designed to enable cabling to support full-duplex Fast Ethernet operation and Gigabit Ethernet.

The main differences between CAT5 and CAT5e can be found in the specifications. The performance requirements have been raised slightly in the new standard.

CAT5e has stricter specifications for Power Sum Equal-Level Far-End Crosstalk (PS-ELFEXT), Near-End Crosstalk (NEXT), Attenuation, and Return Loss (RL) than those for CAT5. Like CAT5, CAT5e is a 100-MHz standard, but it has the capacity to handle bandwidth superior to that of CAT5. With these improvements, you can expect problem-free, full-duplex, 4-pair Ethernet transmissions over your CAT5e UTP.

Category 6
The next level in the cabling hierarchy is Category 6 (CAT6) (ANSI/TIA/EIA-568-B.2-1), which was ratified by the TIA/EIA in June 2002. CAT6 provides higher performance than CAT5e and features more stringent specifications for crosstalk and system noise.

The quality of the data transmission depends upon the performance of all the components of the channel. So to transmit according to CAT6 specs, the jacks, patch cables, patch panels, cross-connects, and cabling must all meet CAT6 standards. (The channel includes everything from the wallplate to the wiring closet.) The CAT6 components are tested individually, and they are also tested together for performance. In addition, the standard calls for generic system performance so that CAT6 components from any vendor can be used in the channel.

CAT6 channel transmission requirements should result in a Power-Sum Attenuation-to-Crosstalk Ratio (PS-ACR) that’s greater than or equal to zero at 200 MHz.

In addition, all CAT6 components must be backward compatible with CAT5e, CAT5, and CAT3. If different category components are used with CAT6 components, then the channel will achieve the transmission performance of the lower category. For instance, if CAT6 cable is used with CAT5e jacks, the channel will perform at a CAT5e level.

Industry standards
The advantage of sticking to the industry standards is the knowledge that your cabling will be compatible with standards applications. But the standards are always being improved upon, and it takes time to ratify a new standard. Often, as with CAT6, the final standard may be different from the proposed standard. For the latest information, contact our FREE Tech Support.

Twisted-Pair Cable Specifications Comparison
Frequency — CAT5, CAT5e: 100 MHz;
CAT6: 250 MHz;
CAT7 (Proposed): 600 MHz
Attenuation (min. at 100 MHz) — CAT5, CAT5e: 22 dB;
CAT6: 19.8 dB;
CAT7 (Proposed): 20.8 dB
Characteristic Impedance — All: 100 ohms ± 15%
NEXT (min. at 100 MHz) — CAT5: 32.3 dB;
CAT5e: 35.3 dB;
CAT6: 44.3 dB;
CAT7 (Proposed): 62.1 dB
PS-NEXT (min. at 100 MHz) — CAT5: no specification;
CAT5e: 32.3 dB;
CAT6: 42.3 dB;
CAT7 (Proposed): 59.1 dB
ELFEXT (min. at 100 MHz) — CAT5: no specification;
CAT5e: 23.8 dB;
CAT6: 27.8 dB;
CAT7 (Proposed): not yet specified
PS-ELFEXT (min. at 100 MHz) — CAT5: no specification;
CAT5e: 20.8 dB;
CAT6: 24.8 dB;
CAT7 (Proposed): not yet specified
Return Loss (min. at 100 MHz) — CAT5: 16 dB;
CAT5e: 20.1 dB;
CAT6: 20.1 dB;
CAT7 (Proposed): 14.1 dB
Delay Skew (max. per 100 m) — CAT5: no specification;
CAT5e: 45 ns:
CAT6: 45 ns;
CAT7 (Proposed): 20 ns