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Twisted Pair flamephoenix compiled an overview of two, three model specifications, performance indicators Fourth, the test data five commonly used twisted pair cables six over Category 5 cabling system I. Overview Twisted Pair (TP: Twisted Pairwire) is integrated wiring Engineering is the most commonly used transmission medium. Twisted pair consists of two copper wires with an insulating protective layer composition. The extent of the two insulated copper wires twisted by a certain density with each other, can reduce signal interference, each wire wave radiation in the transmission line will be another root offset waves emitted. Twisted pair generally consists of two 22 to 26 insulated copper wire wound from each other. If one or more pairs of twisted pair in an insulating sleeve became twisted-pair cable. In the twisted-pair cable (also known as twisted pair cable), the different pairs have different twist length, in general, twist length 38.1cm to 14cm in inner counter-clockwise twist, adjacent pairs twist length 12.7cm above. Compared with other transmission media, twisted pair transmission distance, channel bandwidth and data transfer speed, etc. are subject to certain restrictions, but the price is relatively cheap. Currently, twisted-pair unshielded twisted pair can be divided into (UTP: Unshilded Twisted Pair) and shielded twisted pair (STP: Shielded Twisted Pair). While UTP is mainly used to transmit analog audio information, it is equally applicable to a digital signal transmission, especially for short distance transmission of information. During transmission, the signal attenuation is relatively large, and waveform distortion. LAN using twisted pair wire bandwidth depends on the quality, length and transmission technology used. As long as careful selection and installation of twisted pair, you can reach millions of bits per second transfer rate and reliable within the limited distance. When the distance is very short, and using special electronic transmission technology, transmission rates up to 100Mbps ~ 155Mbps. Because it will be surrounded by radiation using twisted pair transmission of information when the information is easy to know, so to take extra price to be shielded. Shielded twisted-pair cable wrapped outer layer of aluminum foil to reduce radiation, but it does not completely eliminate the radiation. Shielded twisted pair relatively high prices, difficult than unshielded twisted-pair cable installation. Similar to the coaxial cable, it must be equipped with special coupling support shielding function and the corresponding installation technology. But it has a higher transmission rate can reach 100 meters 155Mbps. In addition, the unshielded twisted-pair cable has the following advantages: (1) unshielded jackets, small diameter, saving the space occupied; (2) light weight, easy to bend, easy to install; (3) or to minimize crosstalk eliminated; (4) a flame retardant; (5) the independence and flexibility for structured cabling. Second, the specification model EIA / TIA defines five different quality models for the twisted-pair cable. Computer network cabling using the third, fourth, five. The five models are as follows: 1, the first category: mainly used for transmission of voice (a type of standard is mainly used for the early eighties before the telephone wire), not for data transmission. 2, the second category: transmission frequency of 1MHz, for voice transmission and a maximum transfer rate of data transmission of 4Mbps, common in the use of a token-passing protocol specification 4Mbps old Token Ring. 3, the third category: that is currently specified in the ANSI and EIA / TIA568 standard cable. The cable transmission frequency of 16MHz, for voice transmission and a maximum transfer rate of 10Mbps data transmission, mainly for 10base-T. 4, the fourth category: the transmission frequency of such cables is 20MHz, for voice transmission and a maximum transfer rate of 16Mbps data transmission, mainly for token-based LAN and 10base-T / 100base-T. 5. The fifth category: class cable increased winding density, a high-quality jacket insulation materials, transmission frequency of 100MHz, for voice transmission and a maximum transfer rate of 100Mbps data transmission, mainly for 100base-T and 10base-T network, which is most commonly used Ethernet cable. Twisted pair shielded twisted pair is divided into two major categories of unshielded twisted pair. Was divided in two categories 100 ohm cable, twin cable, large number of cables and 150-ohm shielded cable. There are many specific models, as shown in FIG. The figure represents AWG American Wire Gauge. Third, performance indicators for twisted pair, users are most concerned about it is to characterize the performance of several of its indicators. These indicators include attenuation, near-end crosstalk, impedance characteristics, distributed capacitance, DC resistance. (1) attenuation Attenuation (Attenuation) is a measure of signal loss along the link. The length of the cable attenuation relationship, with increasing length, signal attenuation increases. Attenuating "; db"; for the unit, indicating that the source signal is transmitted to the receiver side signal strength ratio. Since the attenuation varies with frequency, therefore, should be measured attenuation of all frequencies within the range of applications. (2) near-end crosstalk crosstalk near end crosstalk and far-end crosstalk points (FEXT), Tester is measuring NEXT, due to line losses, and therefore less affected by the magnitude FEXT. Near-end crosstalk (NEXT) loss is a measure of a UTP link signal coupling from one pair to another pair wire lines. For UTP link, NEXT is a key performance indicator, is also an indicator of the most difficult to accurately measure. With increasing signal frequency, the measurement will increase the difficulty. NEXT crosstalk value does not mean that generated at the proximal point, it just means that the proximal point of the measured crosstalk values. This value will vary with the cable length becomes, the longer the cable, and its value becomes. At the same time the sender signal is also attenuated, the crosstalk on the other line on the relatively smaller. Experiments show that only measured in the 40 meters was NEXT is more realistic. If the other side is far in the 40 meters of the information outlet, then it will produce some degree of crosstalk, but the tester may not be measured until the crosstalk value. Therefore, the best in both endpoints were measured NEXT. Now tester is equipped with the appropriate equipment, such link can be measured at one end of the NEXT value at both ends. NEXT test results see Table 1 and Table 2. Table 1 is the maximum length of the various connection attenuation at various frequencies limit frequency (MHz) maximum rate minus 20oC channel (100 m) link (90 meters) 3 Class 4 Class 5 Class 3 Class 4 Class 5 Class 1 4.2 2.6 2.5 3.2 2.2 2.1 4 7.3 4.8 4.5 6.1 4.3 4.0 8 10.2 6.7 6.3 11.5 7.5 8.8 6 5.7 10 7.0 10 6.8 6.3 16 14.9 9.9 9.2 13.2 8.8 8.2 2011 10.3 9.9 9.2 25 11.4 10.3 31.25 12.8 11.5 62.5 18.5 16.7 10 024 21.6 Table 2 NEXT attenuation limit frequency (MHz) The minimum NEXT channel at a specific frequency (100 m) link (90 meters) 3 Class 4 Class 5 Class 3 Class 4 Class 5 Class 1 39.1 53.3 60.0 40.1 54.7 60.0 4 29.3 43.3 50.6 30.7 45.1 8 24.3 38.2 51.8 45.6 25.9 40.2 22.7 36.6 44.0 24.3 47.1 10 38.6 45.5 16 19.3 33.1 40.6 21 35.3 42.3 20 31.4 39.0 25 37.4 39.1 31.25 33.7 40.7 35.7 37.6 62.5 30.6 32.7 100 27.1 29.3 The above two indicators are the main contents TSB67 testing But some models of testers can also give DC resistance, characteristic impedance, attenuation crosstalk ratio and other indicators. (3) DC resistance TSB67 no such argument. DC loop resistance will consume part of the signal, and convert it into heat. It refers to a pair of wire resistance and, 11801 specifications of twisted pair is not greater than 19.2 ohms DC resistance. Differences between each pair can not be too large (less than 0.1 ohm), or that poor contact, you must check the connection point. (4) The characteristic impedance of the loop DC resistance is different, characteristic impedance including resistance and frequency inductive impedance and capacitive impedance 1 ~ 100MHz, which is the electrical performance and insulation distance between a pair of wire-related. All kinds of cables have different characteristic impedance, and twisted-pair cable is 100 ohms, 120 ohms and 150 ohms several. (5) attenuation crosstalk ratio (ACR) in a certain frequency range, the ratio between the amount of crosstalk attenuation is another important parameter reflecting the performance of cable. ACR sometimes signal to noise ratio (SNR: Signal-Noice ratio) said it calculated the magnitude of the difference between NEXT attenuation of the worst. ACR larger value indicates a stronger anti-interference ability. General system requires at least greater than 10 dB. (6) the quality of the cable characteristics of the communication channel is determined by its cable characterization. SNR is taking into account the interference signal, a data signal strength metric. If the SNR is too low, it will cause the data signal is received, the receiver can not distinguish between the data signal and the noise signal, and ultimately lead to data errors. Therefore, in order to limit data errors within a certain range, you must define a minimum acceptable SNR. Fourth, the test data 100 ohm unshielded twisted pair has four pairs of Category 3, 4, line 5 cable and super Category 5 points. The main performance indexes of attenuation, distributed capacitance, DC resistance, DC resistance offset value, the impedance characteristics, return loss, near-end crosstalk. Standard Test data shown in Table 1. Table 3 twisted-pair standard test data (a) the type of rate reduction (in db) distributed capacitance (in 1khz metering) DC resistance measurement Measurement 20oC timing correction DC resistance value deviation of 20o Class 3 <2.320sqrt (f) + 0.238 (f) <330pf / 100 米 <9.38 ohm / 100 m 5% Class 4 <2.050sqrt (f) + 0.1 (f) <330pf / 100 米 above 5% 5 Class <1.9267sqrt (f) + 0.075 (f ) <330pf / 100 米 above 5% (b) the type of impedance characteristics 1Mhz reference frequency to the highest return loss measurement length> 100 m NEXT measuring length> 100 m 3 class 100 ohms + 15% 12db 43db 4 categories above 12db Ibid 23db 64db 58db 5 class five commonly used twisted pair cables cabling most commonly used twisted pair cables are the following: 1,5 class four pairs of unshielded twisted pair which is a real American Wire Gauge 24 core bare copper conductor, vinyl fluoride do insulation, transmission frequencies up to 100MHz. Wire composition shown in Table 4, the physical structure shown in Figure 2. Table 4 wire color coding line color code 1 White / Blue @ Blue 2 White / Orange // Orange 3 White / Green // Green 4 White / Brown Brown // Figure 25 class four pairs of unshielded twisted pair electrical characteristics As shown in Table 5. Among them, ";. 9.38 Ohm MAX Per100m @ 20 ℃"; refers to the constant temperature 20 ℃, each 100 meters of twisted-pair resistance of 9.38 ohms (similar to the following table). Table 55 category four pairs of unshielded twisted pair electrical characteristics of frequency demand (Hz) impedance attenuation value (dh / 100) Max NEXT (db) (worst of) DC impedance 256K - 1.1 - 9.38 ohm MAX.Per 100m @ 20oC 512K - 1.5 - 772K - 1.8 66 1M 85 ~ 115 ohm 2.1 64 4M 4.3 55 10M 6.6 49 16M 8.2 46 20M 9.2 44 31.25M 11.8 42 62.50M 17.1 37 100M 22.0 34 2,5 Class 4 pairs 24AWG100 ohm shielded cable it is AWG bare copper conductor 24 to fluorinated ethylene do insulation, inside a drain wire 24AWG TPG. Transmission frequency of 100MHz, the wire composition as shown in Table 6, the physical structure shown in Figure 3, the electrical characteristics as shown in Table 7. Table 6 mask entry "; 0.002 [0.051] aluminum / polyester tape minimal overlap @ 20 ℃ and a 24AWG TPC drain line"; the meaning is: shielding layer thickness of 0.002 cm or 0.051 inches?. ? @ 20 ℃ representatives at a constant temperature of 20 ℃. Table 6 wire color coding line color code Shield 1 White / Blue @ Blue 0.002 [0.051] aluminum / polyester with minimal overlap @ 20o and a 24AWG TPC drain line. 2 White / Orange // Orange 3 White / Green // Green 4 White / Brown Brown // Figure 35 class four pairs 24AWG100 ohm shielded cable Table 75 category four pairs 24AWG100 ohm shielded cable electrical characteristics of frequency demand (Hz) impedance attenuation value (dh / 100) Max NEXT (db) (worst of) DC impedance 256K - 1.1 - 9.38 ohm MAX.Per 100m @ 20oC 512K - 1.5 - 772K - 1.8 66 1M 85 ~ 115 ohm 2.1 64 4M 4.3 55 10M 6.6 49 16M 8.2 46 20M 9.2 44 31.25M 11.8 42 62.50M 17.1 37 100M 22.0 34 3,5 class four pairs of 26AWG shielded cord It consists of four pairs of wire and a drain wire 26AWG TPC composition, transmission frequencies up to 100MHz. Conductor composition as shown in Table 8, the physical structure shown in Figure 4, the electrical characteristics as shown in Table 9. Table 8 wire color coding line color code mask 1 white / blue // blue 0.002 [0.051] aluminum / polyester foil with some 26AWG TPC drain line. 2 White / Orange // Orange 3 White / Green // Green 4 White / Brown Brown // Figure 35 class four pairs of unshielded wires 24AWG Electrical Characteristics 4.5 class four pairs of unshielded 24AWG cord It consists of four pairs of wire composition for high-speed data transmission, suitable to extend the transmission distance, apply to interconnection or jumper. Transfer rate up to 100MHz. Conductor composition as shown in Table 9, its physical structure shown in Figure 5, the electrical characteristics as shown in Table 10. Table 9 wire color coding line color code 1 White / Blue @ Blue 2 White / Orange // Orange 3 White / Green // Green 4 White / Brown Brown // Figure 55 category four pairs of unshielded cord 24WAG100 Table 10 424WAG100 Category 5 unshielded electrical characteristics of frequency demand cord (Hz) impedance attenuation value (dh / 100) Max NEXT (db) (worst of) DC resistance of 256K - - - 8.8 ohm MAX.Per 100m @ 20oC 512K - - - 772K - 2.0 66 1M 85 ~ 115 ohm 2.3 64 4M 5.3 55 10M 8.2 49 16M 10.5 46 20M 11.8 44 31.25M 15.4 42 62.50M 22.3 37 100M 28.9 34 Six, over Category 5 cabling system over Category 5 cabling system is a non- unshielded twisted pair (UTP) cabling systems, through its "; link"; and "; channels"; performance tests show that it is more than 5 cable requirements TIA / EIA568's. Compared with ordinary CAT5 UTP, attenuation smaller, less crosstalk, and has a ratio higher attenuation and crosstalk (ACR) and SNR (SRL), a smaller delay error, the performance has been improved. It has four major advantages: (1) providing a solid network infrastructure, you can easily transfer, update the network technology. (2) to meet the requirements of most applications, and to meet the low-skew and low crosstalk sum requirements. (3) it is considered for future network applications solutions. (4) plenty of headroom to install and test convenience. Compared with Category 5 cable, Cat5e in near-end crosstalk, crosstalk sum, attenuation and signal to noise ratio has been greatly improved on four main indicators. Near-end crosstalk (NEXT) is the most important criteria for assessing performance. A high-speed LAN in the transmission and reception of data are synchronized. NEXT interference signal when the transmit and receive simultaneously generated when. NEXT unit is db, which represents the ratio of the transmitted signal and the crosstalk signal. In general applications, criteria NEXT method is to use a pair of transmission lines, and the other line is used to receive, such as 10BASET and TokenRing, even 100BASET and 155Mbps ATM. Sometimes, however, you can use the other two pairs of lines, and to the other stations, which can accelerate the speed LAN, such as 622Mbps ATM and 1000BASE-T, not only by a pair of (possible with all of the four pairs of wire) to transfer and reception. Multiple use of a cable transmission line will increase the root cable crosstalk. Now four pairs of Category 5 twisted pair does not consider this situation. Crosstalk sum (Power Sum NEXT) NEXT is generated and transmitted from a plurality of terminals. If a cabling system to meet Category 5 in Power Sum of NEXT requirements, then we can deal with any problems from applications to share the high-speed LAN applications. Super Category 5 cabling system requirements NEXT only Category 5 1/8. SNR (Structural Return Loss) is a measure of the consistency of the standard cable impedance, the impedance changes caused by reflection. Part of the signal energy is reflected to the transmitting side, forming a noise. SRL was measured energy changing standards, since the cable impedance changes caused by structural changes, so that the energy of the signal changes. The less energy is reflected, it means more complete transmission signal, the smaller the noise in the cable. Compared to ordinary Category 5 twisted pair, Cat 5e system operating at a frequency of 100MHz, in order to provide users with near-end crosstalk margin 8db, the user's device disruption only ordinary Category 5 wire system 1/4, so the system more independence and reliability.