The following are a set of answers to some of the most comonly posed questions regarding cabling, structured systems and networking in general.
Q1. What are the different categories of cabling and what do they define ?
· Cat 1: Currently unrecognized by TIA/EIA. Previously used for POTS telephone communications, ISDN and doorbell wiring.
· Cat 2: Currently unrecognized by TIA/EIA. Previously was frequently used on 4Mbit/s token ring networks.
· Cat 3: Current cable standard, used for data networks utilizing frequencies up to 16 MHz. Popular for 10 Mbit/s Ethernet networks.
· Cat 4: Currently unrecognized by TIA/EIA. Provided performance of up to 20 MHz, and was frequently used on 16Mbit/s token ring networks.
· Cat 6: Defined by the ANSI TIA/EIA 568B-2.1. It provides performance of up to 250 MHz, more than double category 5 and 5e.
· Cat 6a: Operates at frequencies up to 500MHz and provides up to 10Gbit/s
· Cat 7: Draft standard, proposed to include four individually-shielded pairs (ScTP) inside an overall shield. Designed for transmission at frequencies up to 650 MHz.
Q. What is the maximum UTP cable length of a horizontal cable run from patch panel to work area outlet.
A. The maximum UTP cable length of a horizontal cable run from patch panel to work area outlet is 90m. This does not include the patch leads, which can add up to a maximum of 10mtrs.
Q. What is the difference between the standard TIA/EIA 568A and TIA/EIA 568B
A. The only difference between the two standards is that pairs 2 and 3 are reversed.
Q. What are the 6 sub-systems of a structured cabling system ?
· Entrance Facilities
· Equipment Room
· Back Bone Cabling
· Telecommunications Closet
· Horizontal Cabling
· Work Area Components
Q. What is the reason for using a cover cap on the DINTEK keystones ?
A. To ensure that the wires do not move once terminated in the IDC (Insulation Displacement Connector)
Q. What is the maximum allowed untwist on twisted-pair cable pairs.
A. The maximum untwist allowed is 13mm or ½ inch, however the closer the twist are to the connector the better the performance will be.
Q. Is it okay to attach UTP cabling to other services such as fire cabling supports or electrical cable supports ?
A ... No...No... NO !
Q. If I were to measure the amount of tension placed on a UTP cable when pulling... what would the maximum allowable tension be ?
A. The maximum allowed tension allowed is 25pounds or 8-10Kg. Of course, this is hard to measure, so common sense has to be used.
Q. I am installing cabling in the riser of a multi story building. Is it okay to put the cable drum at the bottom and pull the cable to the top?
A. No. The cable should be installed from top to bottom, as this will place the least tension on the cable.
Q. I am installing UTP cabling in ceilings where the temperature may get over 20 deg. Is this okay ?
A. It is better to look at a specific cable with a higher rated jacket than standard UTP, however if this cannot be done, please be aware that cable attenuation may be higher than normal and thus a shorter distance would need to be used than the maximum 90mtrs of UTP.
Q. I am installing a structured cabling system. Can I just run one outlet for each user.
A. No, the minimum no of outlets is 2. One to allow for voice and one for data.
Q. I am running Dintek category 6 UTP cabling on a cable tray. How neat does it have to be ?
A. Actually, within reason, it should not be neat. It needs to be laid in a haphazard fashion, unlike cat5e and lower grades, which could be groomed on the trays. The reason for this is to avoid any instance of Alien Cross talk.
Q. I am running UTP cabling in a narrows space alongside electrical cabling and am wondering how far the electrical and UTP cabling needs to be separated.
A. The minimum separation allowed between electrical cabling and data cabling in a parallel run, is 100mm. Any closer and the risk of EMF interference from the electrical cabling becomes a real risk, which will degrade cabling performance and data integrity.
Q. What is the tightest that I can bend a UTP cable around a corner ?
A. Bend radii must be no less than 4 times cable diameter for four-pair UTP cable.
Q. What is a TDR ?
A. The time domain reflectometer (TDR) measures distances to events, allowing easy location of problems.
Q. What is cross talk ?
A. Crosstalk is the signal coupled to conductors from other conductors that are carrying signal
Q. Why do they call UTP crosstalk NEXT?
A. Because It is measured at the near end of the cable.
Q. What is ACR ?
A. ACR or (Attenutation to Crosstalk ratio) is a measure of the level of the received signal compared to crosstalk.