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Copper Cabling
OMS Cabling System FAQ
Category 6 Cable FAQ
OMS Cabling System FAQ
Q36:What is a Star Topology? Answer: With a star topology,each station has a cable connecting back to a central hub. The most popular networks using a star topology are 10BASE-T Ethernet and Token Ring. Basically every cable is required to begin in a central distribution room and end at its respected jack location no longer than 300ft away. Advantages: A star can simplify troubleshooting because stations can be disconnected from the hub one at a time until the problem is isolated. Further, some hubs are equipped with LEDs that can indicate activity and errors on each port,making it even easier to isolate problems. Disadvantages: It requires more cable to wire a star. A hub failure can knock out the entire network.Stars can be more expensive because of the cost of the hub. Q37:What is an MDF and an IDF? Answer: MDF stands for Main Distribution Frame and IDF stands for Independent Distribution Frame.The MDF is the main computer room for servers, hubs, routers, DSLs, etc. to reside. The IDF is a remote room or closet connected to the MDF by fiber optic cable. In the IDF you can expect to find hubs and patch panels. Q38:What is the difference between different wiring configuration? Answer: Twisted Pair cabling uses an 8-wire modular connector called the RJ-45. The trick is in making sure that you connect the right colored wire to the right pin in the RJ-45. 568A, 568B, 258A and USOC are all standards describing which wire goes on which pin. No matter which cabling wiring configuration is adopted, the pairs are always colored the same. Pair 1 is always blue. Pair Color 1 Blue & Blue with white stripes 2 Orange & Orange with white stripes 3 Green & Green with white stripes 4 Brown & Brown with white stripe The blue wire and the blue wire with white stripes ("blue/white" for short) are twisted together within the cable, and this makes them suitable for carrying.data The various standards define which pair is attached to which pins on the RJ-45. When recalling the wiring configurations, here are some basic rules: * The solid color wires and the striped wires always alternate ** Pin 1 is always a striped wire. *** Pair 1, Blue, is always in the middle on pins 4 & 5. ——568B (AKA 258A) The TIA 568A standard is always the preferred way of terminating cable. It matches the method of terminating cable that Northern Telecom used for ISDN. 568B (AKA 258A) Before the TIA ever met to adopt the 568A standard for cable terminations, AT&T had a very similar standard for terminating their cable, called 258A.258A works just as well as 568A. In fact, the TIA committee decided to include AT&Ts 258A standard, but they called it the 568B standard. 258A and 568B are exactly the same. This is what happens when committees try to make everyone happy.Further, the TIA cabling standard states one may use either 568A or 568B but not both in one cabling system. As long as the wiring configuration is consistent. the system will work fine. Q39:Why are the pairs shuffled around, instead of laid out logically? Answer: Well, they are logical, if you know the background. Ethernet was originally designed to run over the same cabling used by the phone system (AT&T created this as StarLAN), so this design left pins 4/5 available for a phone.If you plug an RJ-11 (4 wire) into this, the middle two pins (2/3) of the RJ-11 would connect to the middle two pins (4/5) of the RJ-45, just perfect for a 1-line phone. If you plug an Ethernet cable into it, pins 1/2 will be used as one pair,and pins 3/6 will be used as another. So, there are no conflicts. USOC is an old standard, used for voice cabling. For 1 & 2 line phones (which use pins 4/5 and 3/6), 568A or 568B will work just as well as USOC. But for Ethernet (pins 1/2 and 3/6), USOC will not work. An Ethernet NIC transmiting signals on pins 1/2 will get troubles because 1/2 are not a pair (not the same color,and not twisted together). So unless one know the cable plant is only for analog voice application and not for any digital voice or ISDN data application, he should avoid using USOC. Q40:When I should use 568A or 568B or USOC? Answer: It does not matter. Both are approved by the TIA/EIA 568. Both have the same performance. What you need to avoid is terminating one end of the run in 568A and the other end in 568B. That will cross pair 2 and 3. Both schemes are shown. Avoid using USOC anywhere in the cable plant. USOC wiring was the pre-data standard for telecommunications. When a LAN NIC transmits on two wires, it expects them to be a pair of wires that are twisted together. Ethernet transmits on pins 1 and 2. Notice that on a USOC cable, they are not twisted together.This greatly increases the crosstalk on the line and causes transmission to be unreliable. Q41:When is Wireless going to replace cabling? Answer: Wireless networks also require cabling. The current applications for wireless solutions are; college campus environments, high schools, shipping companies,hospitals. The wireless solution is a complement solution for a wired. LAN. For instance, in the college campus environments the administration offices would remain cabled, while limited access to the colleges main frame is granted to student sroaming the campus with their laptops. Wireless solutions are also handy in old high schools, hotels, apartments and Condos where ceiling and wall access is limited.IWireless will remain an additional solution but not a replacement for cabled networks. Q42:What is the difference between T568A and T568B wiring schemes? Answer: The only difference is the pin assignments for-pairs 2 and 3 are reversed.TIA recommends using TS68A scheme because it is compatible with USOC 4-wire scheme, but performance-wise it makes no difference. Either wiring scheme can be used, just make sure to stay consistent. Q43:What is the minimum separation distance required between power and communication cables? Answer: Table 10.4.1 in TIA-569 specifies distance requirements based on voltage spikes and the use of metallic or non-metallic trunking. The numbers in this table have been disputed in recent years and will most likely be revised in TIA-569-A. The IEEE electrical regulation requires only a physical barrier between power and communications lines for safety purposes. Q44:Is there a difference between shielded and screened cable? Answer: Yes. Shielded cable (denoted by STP) is most often known as "IBM Type 1"cable. It is defined in TIA-568-A as two individually twisted pairs separated by a shield with a nominal impedance of 150 ohms. Screened cable (called ScTP) can be considered a close relative of UTP. It consists of 4 pairs of 22 or 24 AWG wire enclosed by an outer foil. Q45:There has been some concern recently about "short link resonance".What is it? Answer: There is some connecting hardware on the market that will pass Category 6 requirements in a TSB-40 component test, but will unexpectedly fail Near End Cross Talk (NEXT) when tested in a link of less than 15 meters. TIA is working on additional requirements on connecting hardware that will eliminate this phenomenon. Q46:What is component compliance for Cat 6 product? Answer: Component compliance means that each Category 6 product,including patch panels,patch cords,cable and modular jacks can perform satisfactorily as individual components as outlined in the Category 6 standards. Component compliance means that each product can pass the Cat 6 standard individually with enough headroom of its own.In fact,component compliance is the only way to ensure that a Category 6 network will actually deliver Category 6 performance.Component compliance is different from link and channel compliance.For a link testing, performance is measured from the modular jack at the work a rea,through the horizontal cable to the first patch panel or connecting block of the cross-connect. Link testing does not test the station cord,the equipment cord,or even the additional patch cords, patch panels or connecting blocks in the cross-connect. Channel testing goes one step further by including station cords and equipment cords. Link and channel tests only measure how cabling and connectivity products work together,not the performance of individual components.Link and channel compliance cannot reflect fully the performance of a Category 6 system.Link or Channel testing does not gurantee that an under-performing connectivity product may take advantage of available headroom of the cable product in the channel.Channel tests do not show, for example,how the generous headroom typically available in horizontal cable makes up for the poor performance of a plug.Without component compliance,there is no way that Category 6 products can meet an important part of the Cat 6 standard - backwards compatibility. Q47:What is backwards compatibility? Answer: Backwards compatibility implies an open architecture.which can only be achieved with component compliance.TIA specifically states "next generation cabling,components and mated connections shall satisfy all requirements of their category in addition to all existing lower category specifications." What this means is that mating a Category 6 patch panel with a Category 5e patch cord will result in Category 5e performance. And this means that mating a Category 6 patch panel with a Category 3 patch cord will result in Category 3 performance. Backwards compatibility also implies vendor independence. So, mating a Category 6 patch panel from vendor A with a Category 6 patch cord from vendor B will result in performance that meets Category 6 transmission requirements. Again, this is only possible with a component compliant system. Backwards compatibility is also required for Category 5e and Category 5 products.In fact,TIA states that If different category/class components are to be mixed with category 6/class E components,then the combination shall meet the transmission requirements of the lowest performing category/class component. Q48:What is near-end crosstalk(NEXT)? Answer: Near-end crosstalk(NEXT) is an error condition that can occur when connectors are attached to twisted pair cabling. NEXT is usually caused by crossed or crushed wire pairs. The error condition does not require that the wires be crushed so much that the conductors inside become exposed. Two conductors only need to be close enoughso that the radiating signal from one of the wires can interfere with the signal traveling on the other. Most medium- to high-end cable testers are capable of testing for NEXT errors. Q49:What is ATTENUATION ? Answer: Attenuation is a general term that refers to any reduction in the strength of a signal. Attenuation occurs with any type of signal, whether digital or analog. Sometimes called loss, attenuation is a natural consequence of signal transmission over long distances. The extent of attenuation is usually expressed in units called decibels (dBs).In conventional and fiber optic cables, attenuation is specified in terms of the number of decibels per foot, 1,000 feet, kilometer, or mile. The less the attenuation per unit distance, the more efficient the cable. When it is necessary to transmit signals over long distances via cable, one or more repeaters can be inserted along the length of the cable. The repeaters boost the signal strength to overcome attenuation. This greatly increases the maximum attainable range of communication. Q50:What is ACR? Answer: Attenuation-to-crosstalk ratio (ACR), also called headroom, is the difference, expressed as a figure in decibels (dB), between the signal attenuation produced by a wire or cable transmission medium and the near-end crosstalk (NEXT). In order for a signal to be received with an acceptable bit error rate, the attenuation and the crosstalk must both be minimized. In practice, the attenuation depends on the length and gauge of the wire or cable transmission medium, and is a fixed quantity. However, crosstalk can be reduced by ensuring that twisted-pair wiring is tightly twisted and is not crushed, and by ensuring that connectors between wire and cable media are properly rated and installed. Crosstalk can sometimes be reduced by replacing unshielded twisted pair (UTP) wiring with shielded twisted pair (STP) wiring. The ACR is a quantitative indicator of how much stronger the attenuated signal is than the crosstalk at the destination (receiving) end of a communications circuit. The ACR figure must be at least several decibels for proper performance. If the ACR is not large enough, errors will be frequent. In many cases, even a small improvement in ACR can cause a dramatic reduction in the bit error rate. Q51:What are the Validating Test and the Authentication Test of the cables? Answer: The validating test is used to test whether the lengths of the cables and the connection of the twisted pairs are correct, but it could not be used to test the electric index of the cables. The Authentication Test is used to test the performance of the cables according to some international standard. It includes all the contents of the Validating Test and the indexes of the standard testing cables, such as attenuation and impedance, etc. The Validating Test could not ensure whether the cables can pass through the high-speed data signal of the network, such as 10M or 10MHz. Only the cables fixed achieve the corresponding index so that they can support the signal of 10M or 100M. Q52:What is the link of the cables? Answer: The link of the cables refers to the connection of the cables, including the electric cables, the connector plugs, and the connector jacks or sometimes the patch panels and the coupling. Different standards stipulate different links, ie, the model of the testing. For example, TSB-67 stipulates the Basic Link and the Channel. Especially it emphasizes the link is not equal to the cable. The cable is just one part of the link. If you hope that the cabling system installed could support the bandwidth of 100MHz, the link could achieve the result but the cables could not. Q53:What is the abnormity of the impedance? Answer: The impedance is a kind of electric index of the cables. It should be a constant in the cabling system. If the impedance is not a constant in the use, the phenomena of reflection will occur in the place where the impedance changes. The standard of DS100 and DS2000 the Fluke Company used could show the abnormity of the impedance through the default reflect value of 15%, ie, if the reflection signal goes beyond 15%, it will show that the impedance is in abnormity. Besides, DSP100/2000 could trace out the curve of the special impedance. The perfect curve should be a straight line. If the impedance goes in an abnormal way, there must be a wave crest or a trough in the curve. The wave crest shows that the figure of the impedance becomes bigger, while the trough shows the figure of the impedance becomes smaller. Q54:What are the seven steps of 6 categories Cabling System? Answer: Investigation---Design---Construction---Installation---Testing---Documentation---Maintenance Q55:What is the significance of the standard of 6 categories Cabling System? Answer: It marks the maturity of these six categories products. 2. It unifies all the diversified standards. 3. It tests all the changes of the model. 4. It stipulates the stricter craftworks of the construction. 5. It shows the importance of the authenticated testing. Q56:What is the standard way of connecting the Twisted Pairs? Answer: Generally speaking, the Twisted Pairs are used to construct the Star-shaped network in the Cabling System. Each Twisted Pair connect the network facilities with each other through RJ45 Port Plug fixed in the two ends. The standard way of connecting the Twisted Pairs is not stipulated at random, but to keep the symmetry of the overall arrangement of the whole Cabling System so that it can eliminate the mutual interference of the Patch Cables inside the connector. CAT5e is one of network cables most frequently used in the Cabling System. It can be divided into the Shielded and the Unshielded. If you want to install the Patch Cables outdoor, we advise you of using the Shielded ones. And if you install them indoor, the Unshielded ones will be OK. Because the Unshielded Patch Cables are without the shielded layer, this kind of Patch Cables will be relatively softer than the Shielded ones. But the way of connecting them is similar. Generally speaking, there are 4pairs slimlines bundled in the CAT5e Patch Cables, and they are marked by the different colors. There are two ways of connecting the Twisted Pairs: They are fixed according to the standard of EIA/TIA 568B and EIA/TIA 568A. More details are below: ![]() According to the sequence of T568A: 1 2 3 4 5 6 7 8 green-white green orange-white blue blue-white orange brown-white brown According to the sequence of T568B: orange-white orange green-white blue blue-white green brown-white brown Straight Line: The two ends are connected according to the standard of T568B. Crossover Line: One end is connected according to the standard of T568A, the other T568B. Q57:What are the indexes of products of 6 categories that we can not neglect? Answer: Many key indexes of products have been neglected when the users choose the products. But it is very critical for the quality of the construction. Besides, it is also very helpful to improve the qualities of the cables wholly. 1. Which kind of value it is, the Typical Value or the Guaranteed Value? Generally speaking, the Typical Value is an affirmatory value which means it will be achieved even if the products are not good enough. In fact, the actual testing value must go over the lowest level but will not be lower than it. Judging from the definitions of the Typical Value and the Average Value, the actual testing value sometimes goes over the Typical Value and sometimes goes under it. But what the users are always concerned about is what the lowest value is on earth. Generally speaking, the Guaranteed Value is lower than the Typical Value at about 3-5dB. Therefore, it is wrong to compare the Guaranteed Value of products A with the Typical Value of product B. What the users should compa with is the Guaranteed Value of the two kinds of products, because the Guaranteed Value means that the actual performance of the two kinds of products will be much better than the lowest level. It is impossible that the actual performance is lower than the Guaranteed Value, so only the Guaranteed Value can make the users feel reassuring. A manufacturer who holds the credit standing should show the Guaranteed Value to the users, because it is a kind of promise. 2. Are both the Long Channel and the Short Channel suitable for the actual use? Most of us feel that the index of the Long Channel is better than the Short Channel, but actually the case is not like this. About some parameters, the Short Channel is not good as the Long Channel, because the indexes that many manufacturers give are based on the channel with the length of 100m. However, it cannot reflect the needs of users really. In fact, in most cases the lengths of the channels are between 30m and 40m. When the users buy the products, the two points below should be considered: 1. Does the manufacturer provide the users with the corresponding parameters? 2. Are both the Long Channel and the Short Channel suitable for the actual use? Only the products of six categories meet all the demands so that they can give the users the guarantee.Additionally, all the series of Addison products meet the demands that the newest test stipulates of the six categories Cabling System no matter what kind of channel is, the Long Channel or the Short Channel.. 3. The indexes of the performance are based on how many times are the products tested? Ten or thousands of times? If the indexes of the performance are just based on more than ten times of testing results (or even some manufacturers stipulate the indexes of the performance only by a certain test), such testing results can not represent the actual performance at all. Only the indexes of the six categories measure up the testing results for thousands of times so that the quality can be guaranteed. 4. Is it a whole frequency strip or a single frequency? Besides all the problems above, all the indexes should point to the lowest value of the whole frequency strip. If a manufacturer just provides the indexes of performance on a certain frequency, the users should consider whether it is safe to be used. Usually, these indexes the manufacturer provide with are the best in a given frequency. At least, the indexes in other frequencies are not as good as those in that given frequency. Q58:What is the difference between 10BASE-T, 100BASE-T and 1000BASE-T? Answer: 10BASE-T is the IEEE standard that defines the requirement for sending information at 10 Mbps on unshielded twisted-pair cabling, and defines various aspects of running Ethernet on this cabling. 100BASE-T is the IEEE standard that defines the requirement for sending information at 100 Mbps on unshielded twisted-pair cabling, and defines various aspects of running base-band Ethernet on this cabling. 1000BASE-T (also called gigabit Ethernet) is the IEEE standard that defines the requirement for sending information at 1000 Mbps on unshielded twisted-pair cabling, and defines various aspects of running base-band Ethernet on this cabling Q59:What is a cross-over cable? Answer: A cross-over cable is a segment of cable that crosses over pins 1&2 and 3&6. This cable is normally used to connect two PCs without the use of a hub, or can be used to cascade two hubs without using an uplink port. Some DSL modems require a crossover cable to the PC or hub they are connected to. Q60:What are the maximum lengths for cables? Answer: For Solid UTP: Fast Ethernet 100baseT 100 Meters (328 feet) Twisted Pair Ethernet 10baseT 100 Meters (328 feet) Recommended maximum lengths for Patch Cables made from stranded cable: Fast Ethernet 100baseT 10 Meters (33 feet) Twisted Pair Ethernet 10baseT 10 Meters (33 feet) Q61:What is EMI and how to prevent it? Answer: EMI stands for Electro-Magnetic Interference. It is potentially harmful to your communications system because it can lead to signal loss and degrade the overall performance of high-speed, CAT-5e cabling. EMI is interference in signal transmission or reception and is caused by the radiation of electrical or magnetic fields which are present near power cables, heavy machinery, or fluorescent lighting. Avoiding EMI is as simple as not laying your network cable within 12" of electrical cable, or if needed switching from UTP to more expensive shielded cable. |