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SOHO Simple Cable FAQ v3.0


In this version:

Intro

This is not the only cabling FAQ on the Internet, however, most of the other FAQ's I've seen tend to cater more to the experienced cable installer, whereas this FAQ is targeted towards the person who wants to get an understandable introduction to cabling. I've taken great care to ensure all information here is accurate, but there is always the possibility for error. If you see something that you think is wrong, please send an e-mail to me.

Disclaimer

This information is provided free of charge. No fees may be charged for the distribution or publication of this material. These documents are (c)1996-1999. This information is provided as a guideline only, and may be superceded by local codes or ordinances. Check with your local electrical codes before doing any wiring. This information may only be copied, reproduced, or otherwise duplicated in it's entirety.

Terms and Definitions

AWG= American Wire Gauge, for rating the 'size' of a wire, the smaller the number, the larger the size.

BNC = A twist-lock connector used in coaxial cable networks.

Coaxial Cable = A cable with one inner conductor, and an outer shield insulated from one another by a dielectric foam, used mostly in CATV, and 10Base2 Ethernet

Connecting Block = A Plastic block containing metal clips for connecting wire runs in a distribution closet.

CMS = Cable Management System, refers to the products used to neaten-up a cable plant.

Concentrator = Basically a high-density hub, usually designed to allow for future expansion.

Cross-Over cable = Usually referring to Ethernet. A cable that crosses the transmit and receive pins appropriately so that two devices can communicate directly without the use of a hub, or similar intermediate device.

CSMA/CD = Carrier Sense Multiple Access / Collision Detect. Before a device sends a packet it checks to see if another device is already transmitting. If the line is clear it will send it's packet. If two devices start sending at the same time a 'collision' is caused, the devices can detect this collision, and will each wait a random amount of time before re-retrying. This is the access method used by Ethernet.

DEMARC = Demarcation point, identifies the division of a loop or circuit responsibility, where the telco's responsibility ends, and the subscribers begins.

F Connector = Connector type used in cable-tv connections. Can be threaded or push-on type.

FOIRL = Fiber Optic Inter-Repeater Link

Full-Duplex = Data can travel in both directions at the same time, using 100% of available bandwidth.

Half-Duplex = Data travels in one direction, or the other, using 100% of available bandwidth.

Hub = Usually referring to Ethernet. Multiple cables from PC's, servers, etc are all plugged into the hub, which retransmits signals from one device to all other devices on the hub. If more ports are needed than are present on your hub, multiple hubs can be cascaded together, through the use of a cross-over cable (see below), a special port designated on the hub, usually as 'MDI', or with a 'cascading' cable and port.

Horizontal Cable = The portion of a cable system that extends from the wall jack to the device (phone or PC typically). Also refers to the cable used to connect a hub or PBX to a patch panel.

HVAC = Heating, Ventilating, and Air Conditioning systems.

IDC = Insulation Displacement Connector. This is the connector type found in most network termination equipment. An IDC works by removing the insulation on a wire as the connection is made, usually by either piercing the insulation, as is the case with RJ jacks, or by using a special tool to force the individual wire between two closly placed 'blades' of a connector, where the insulation is removed as the wire is forced between the blades. This type of connector speeds termination of wire, and allows for a simple, reliable connection.

ISDN = Integrated Services Digital Network. ISDN lines typically contain two 'B' channels, and one 'D' channel:
B Channel = Bearer Channel, 64Kbs in the US, this is the channel that carries the user data.
D Channel = Data Channel, 16Kbs, this is the channel that carries signalling information, used by the ISDN network to connect or disconnect 'B' channels.


MAC Address = A unique Hex number assigned to a device to identify it on the network. Like a serial number. MAC addresses are 6 bytes long, the first three bytes are unique to each manufacturer, the last three are a sequential number.

Multi-Mode (MM) = Refers to fiber-optic cable. Common size is 62.5/125. This means the core (or actual fiber) is 62.5 microns, the cladding is 125 microns. Multi-Mode fiber is used in most typical LAN applications, and is limited to a distance of 2Km. As it's name implies multl-mode can carry multiple 'conversations' based on different light input attenuations.

MUX = MUltipleXer . A MUX takes multiple low-bandwidth channels, and combines them into one channel to be carried over a single high-bandwidth carrier. At the opposite end of the circuit another MUX/DEMUX converts the high-bandwidth signal back into it's multiple low-bandwidth channels.

NIC = Network Interface Card. Any ethernet, arc-net, or token ring card.

Node = Refers to a device on a network, other than a hub. Ie: PC, router, bridge, sniffer, printer.

Patch Cable = A short length of network cable used to connect two devices together.

Patch Panel = A device where data cables are terminated. Patch panels allow wiring to be easily re-configured based on need. Patch panels are more for convenience and are not needed in order to make a successful data network.

Plenum = An air-return area in a HVAC system. Plenum is NOT a type of cable coating, but rather a rating of cable for use in a 'plenum' area. Some plenum grade cable is PVC jacketed.

POTS = Plain Old Telephone Service (really). A regular residential analog phone

PVC = A common cable jacket material.

Raised Floor = Usually found in computer rooms. Floor panels are set on risers usually 10"-12" above the actual floor, used to route cables under equipment, and provide a plenum for air conditioning.

RJ-11 = Registered Jack 11, a standard phone jack.

RJ-45 = Registered Jack 45, refers to a type of jack, similar to a phone jack, only wider.

Riser = A vertical shaft or conduit used to route cables between floors.

Router = A device that is used to connect two distant LAN's via a WAN

SC = A type of fiber connector. Terminates one pair of fiber into one jack. Looks like two squares side-by-side. SC connectors make a 'click' when they are seated, thus SC is often remembered as Stick and Click.

Single-Mode (SM) = Refers to fiber-optic cable. Common core is 5-10 microns. SM fiber has a much longer working distance, but because of its small core size requires the use of a more precise transmitter light source, ie: laser. SM is used in most WAN applications, such as Telco distribution. Because of it's small core size, single-mode fiber can carry only one conversation.

Simplex = Data travels in one direction only.

ST = Type of fiber connector. Terminates each fiber individually. Looks like a mini BNC connector. ST is often remebered as Stick and Twist.

Stackable = Refers to Ethernet hubs that can be connected together, usually only with similar brands/models, so that the number of ports is increased, without adding additional hops.

Switch = Allows for a large network to maintain an effective data throughput by segmenting it into multiple parts, then passing traffic only to the segment that contains the destination host, thus eliminating traffic on the other segments.

TDR = Time Domain Reflectometer (used to measure cable length based on reflection time of a generated signal)

Tone Generator and Inductive Amplifier = The tone is connected to one end of a cable, and places a (typical) 2 kHz audio tone on the cable. The inductive amplifier can detect this signal without having to cut or damage the cable being tested. The inductive amplifier usually has a range of about 1"-4" from the cable. Typically used to identify or trace cables.

Twin-Ax = Twinaxial Cable. Similar to coax, but with two internal conductors, surrounded by a common shield.

USB = Universal Serial Bus. An emerging standard for (mainly) PC serial communications. Runs at 12Mbs, supports up to 127 devices via a daisy-chain method, supports hot connections.

Wiremap tester = Checks cables for wiring errors, such as: open or short circuits, reversed pairs, crossed pairs, etc. Wiremap testers may be complex digital devices, or simple analog continutiy sensing devices.

Common Questions / Answers.

Q: Can I run voice and data (ethernet) in the same cable?
A: This is done by some, and usually with success. But the correct answer, is no, you should not do this. It opens your network up to interference and performance problems (when your phone rings the line is carrying a 90V ac signal. ) as well, it may limit the future flexibility of your network. You also run the slight risk that a 40-100VDC telephone signal might get inadvertantly connected to your netowrk card. It is best to think of each cable that is to be used for networks as a single purpose device. Your network will NOT be Cat5 compliant if you do this

Q: Can I run multiple voice lines in the same Cat3/5 cable?
A: Yes, this is not likely to cause any problems.

Q: 10BaseT only uses 2 pairs of a 4 pair cable, can I use the other 2 pairs for another network run?
A: Usually. This will limit the working distance of your cable run, and may cause problems. It will also violate TIA specs, but will work in a pinch. Best to run another cable.

Q: What does 'Cat 5' mean?
A: Cat 5 is a designation for a cable run that complies with certain standards regarding termination (end connectors), attenuation specs, distance, response, etc. The actual cable alone is only one of many parts to conforming to a 'Category 5' specification.

Q: I only have to install a few outlets, do I really need a punch-down tool, or can I use a screwdriver, or other 'tool'?
A: Actually, you shouldn't use anything but a good impact punchdown tool for regular punch-down connectors. However, some companies like AMP, Panduit and ICC do have tool-less outlets. These come with a little plastic lever, or similar, you place all wires in their respective locations, put a plastic cap over the wires, then use the lever tool to snap the plastic cap over the wires. Response so far has been that these outlets work great, and usually only cost about $.25 more than a regular outlet. Using a screwdriver or other non-standard punchdown device may damage or disformthe IDC 'prongs' that make the electrical connection to your cable, causing all sorts of future headaches.

Q: Where is Pin #1 located?
next to pin#2

Q: Can I connect two 10BaseT computers directly, without a hub?
A: Yes, via the use of a crossover cable, the pinout is in the cable tables.

Q: Can I connect more than 2 10BaseT computers without a hub?
A: Sort of. If you have a machine that can route packets (NT, Linux, Unix, Novell) then you can install multiple cards in the server, and connect the individual workstations via crossover cables. This method will quickly become more expensive than just buying a small hub.

Q: I have a 10Base2 network and I want to connect it to a 10BaseT, can I? How?
A: They can be connected in one of the following ways:
1:Buy a workgroup hub with an AUI (Attachment Unit Interface) port, this looks like a game port. Buy a transceiver to go from 10B2 to 10BT, about $25.00, connect the 10B2 to the xceiver,to the hub. Connect your 10BT devices to the hub.
2:If you have a server that can route packets, install a 10B2 and 10BT card in the server, then enable routing/forwarding.

Q: Can I connect two buildings with 10Base(X).
A: Yes, but it is HIGHLY recommended to use fiber, this will eliminate ground loops, mismatched ground potentials, and the possibility of a power surge affecting both building via the network cable.

Q: Can I use a telephone-type splitter on a 10BaseT line to connect two devices to one hub port?
A: If you could do that, there wouldn't be much reason to buy a hub with more than 4 ports, now would there? No, you cannot do this.

Q: I thought I had heard of a company that sold splitters for this purpose?
A: Some places do have splitters that will allow you to use the two unused pairs in a 4 pair Cat5 run for an additional network connection. You must use these splitters on either end of the cable, and they will require you to use another hub port. Although it works it will violate TIA specs, and is not recommended. It WILL NOT work with 100Mb ethernet..

Q: I already have 75ohm (CATV) coax throughout my location, can I run a coax ethernet on this cable?
A: No, not really. Ethernet requires a cable with a 50ohm impedance to operate. There are some companies that sell a sort of balun to do this, but the results are unreliable. (Why does it seem there is always somebody who sells something to get around 'doing-it-right'?)

Q: What is the best cable to use for wiring or extending my POTS line?
A: Although a POTS line will work on just about anything, it's best to use a Cat3 minimum cable to allow for some future bandwidth expandability of the line. Run Cat5 if possible.

Q: What is a 'stackable' hub, why would I want one?
A: Stackable means that two or more hubs can be connected via a special cable so that the number of ports is increased, without adding more 'hops' to the network. The typical way to add another hub to a network is by using a regular Ethernet cross-over cable to go between one port on each hub. This creates a 'hop', which can cause more delay in the network. For two hubs, this hop will hardly be noticed, with many hubs, the additional hops may violate Ethernet specs. Typically you want 4 (or less) hops between any two nodes on the network.

Q: How should the hub to patch-panel be wired? How about patch-panel to outlet? Outlet to PC?
A: When installing cable, ALL cables should be wired as straight-through. Cable is a 'passive' device. It generally should not alter the signal in any way, nor should it re-arrange pin-outs in any way, these functions are left to the 'active' devices likes hubs.

Q: I'd really like to cable my house right, but it seems kind of expensive, is there anyway to cut corners without hindering the performance?
A: Yes, actually there are a number of things you can do:
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