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Glossary of Network and Cable Industry Terms


Amplifier

A device that boosts the strength of an electronic signal. In a cable system, amplifiers are spaced at regular intervals throughout the system to keep signals picture-perfect regardless of how far you live from the head end.

Attenuation

Attenuation is the loss of signal over the length of a network link due to the resistance of the wire plus other electrical factors that cause additional resistance (impedance and capacitance for example). A longer cable length, poor connections, bad insulation, a high level of crosstalk, or EMI can all increase attenuation. For each category of cable, the TIA-568B standard specifies the maximum amount of attenuation that is acceptable in a network link.

Bend Radius

Bend radius is the minimum radius a cable can be bent without kinking it, damaging it, or shortening its life. The minimum bend radius for Category 5, 5e, and 6 cable is four times the cable diameter, which is approximately 1 inch. When cabling is bent beyond this specified minimum bend radius, it can cause transmission failures. All pathways must maintain the minimum bend radius wherever the cable makes a bend.

Coaxial Cable

Copper or copper-sheathed aluminum wire surrounded by an insulating layer of polyethylene foam, used by cable television systems. The insulating layer is covered with tubular shielding composed of tiny strands of braided copper wire, or a seamless aluminum sheath, and protective outer skin. The wire and the shielding react with each other to set up an electromagnetic field between them. This system reduces frequency loss and gives cable its great signal-carrying capacity.

Converter

Device that is attached between the television set and the cable system that can increase the number of channels available on the TV, enabling it to accommodate the multiplicity of channels offered by cable TV.

Cross-Modulation

A form of television signal distortion where modulation from one or more television channels is imposed on another channel or channels.

Crossover Cable

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 calbe to the PC or hub they are connected to.

Crosstalk

Crosstalk is the "bleeding" of signals from one pair in a cable onto another pair through induction (wires need not make contact because signals are transferred magnetically). Crosstalk is an unwanted effect that can cause slow data transfer, or completely inhibit the transfer of data signals. Crosstalk is minimized by the twisting of the pairs in the cable. Fiber Optic cable is the only cable medium that is 100% immune to the effects of crosstalk or EMI.

Delay Skew

Only a critical parameter in high-speed networks that transmit data using multiple pairs, Delay Skew is the difference in time between the fastest arrival of a data signal on a pair and the slowest. Signals divided over multiple pairs need to reach the other end within a certain amount of time to be re-combined correctly.

Distortion

The departure, during transmission and amplification, of the received signal wave form from that of the original transmitted wave form.

Drop Cable

Generally 330 feet or less, of coaxial cable, starting at a tap and continuing on to the subscribers connection. Or coaxial cable that connects to a residence or service location from a directional coupler (tap)on the nearest coaxial feeder cable.

Dual Cable

Two independent distribution systems operating side by side, providing double the channel capacity of a single cable.

Duplex

In a communications channel, the ability to transmit in both directions.

Electronic Industries Association (EIA)

A voluntary body of manufacturers which, among other activities, prepares and publishes standards.

EMI

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 switching from UTP to shielded cable.

Ethernet

The most popular LAN technology in use today. The IEEE standard 802.3 defines the rules for configuring an Ethernet network. It is a 10Mbps, 100Mbps, or 1000 Mbps CSMA/CD baseband network that runs over thin coax, thick coax, twisted pair or fiber optic cable.

F-Connector

The final piece of hardware (familiar to subscribers) on a drop cable. It is cylindrical with a center pin sticking out, that plugs into the set-top box, cable ready TV or VCR.

Fiber Node

A point of interface between a fiber trunk and the coaxial distribution.

Fiber Optics

(1) Very thin and pliable tubes of glass or plastic used to carry wide bands of frequencies. (2) Transmission medium that uses glass or plastic fibers vs. other, copper-based wires to transmit data or voice signals. Fiber-optic cable offers much greater capacity and transmission speeds than traditional mediums.

Full Duplex

Means that communications between two end points can take place at the same time. A standard voice telephone call is a full-duplex call because both parties can talk at the same time and be heard. A short wave radio conversation between two people is not full duplex because the person talking has to press the transmit button to talk, and while he is talking he can not hear the other party.

Group Delay

The difference in transmission time between the highest and lowest of several frequencies through a device, circuit or system.

Half Duplex

Two-way transmission, one way at a time.

High-bandwidth Digital Content Protection (HDCP)

A specified method from Intel for protecting copyrighted digital entertainment content that uses the Digital Video Interface (DVI) by encrypting its transmission between the video source and the digital display (receiver). The video source might be a computer, set-top box, or DVD player, and the digital display might be an LCD display, television, plasma panel or projector.

High Definition Multimedia Interface (HDMI)

A specification that combines video and audio into a single digital interface for use with DVD players, digital television (DTV) players, set-top boxes, and other audiovisual devices. The basis for HDMI is High Bandwidth Digital Content Protection (HDCP) and the core technology of Digital Visual Interface (DVI). HDCP is an Intel specification used to protect digital content transmitted and received by DVI-compliant displays.

High Definition Television (HDTV)

A television signal with greater detail and fidelity than the current TV systems used. The USA currently uses a system called NTSC. HDTV provides a picture with twice the visual resolution as NTSC as well as CD-quality audio. Or television that substantially exceeds NTSC, PAL or SECAM in resolution and quality.

Institute of Electrical and Electronics Engineers (IEEE)

A voluntary organization which, among other things, sponsors standards committees and is accredited by the American National Standards Institute (ANSI).

Interconnect

Two or more cable systems distributing a programming or commercial signal simultaneously.

International Electrotechnical Commission (IEC)

An international standards body.

International Organization for Standardization (ISO)

An international standards body, commonly known as the International Standards Organization.

Jumper Cable

Short length of flexible coaxial cable used in older cable television systems to connect system coaxial cable to amplifiers or other cable television components.

Multimode

When a photon careens off the optical fiber wall as it goes from one end to the other. Other photons take different paths. There are approximately 200 different paths in a single fiber.

Ohm

The standard unit of resistance, reactance and impedance. A resistant of 1 ohm will conduct 1 ampere of current when a voltage of 1 volt is placed across it.

Packet

A series of bits containing data and control information, including source and destination node addresses, formatted for transmission from one node to another.

Patch Cable

A Patch Cable is a cable assembly that consists of a length of UTP cable with an RJ45 male connector crimped onto each end. This cable assembly is used to provide connectivity between any two RJ45 jacks. The two most common uses for patch cables are for connecting patch panel ports to other patch panel ports or to switch ports, and for connecting the work area outlet (jack) to the computer or other networked device.

Patch Panel

A Patch Panel is a series of RJ45 jacks condensed onto a single panel. Common panel configurations include 12, 24, 48, and 96 ports. Patch panels are typically deployed where horizontal cables converge, and are used to interconnect or crossconnect links to a network switch or hub.

PSELFEXT

Like PSNEXT, PSELFEXT is the sum of the ELFEXT induced on a pair from all other adjacent pairs. PSELFEXT is only critical in high-speed networks that transmit data over multiple pairs.

PSNEXT

PSNEXT is the sum of the NEXT induced on a pair from all other adjacent pairs. PSNEXT is a more stringent measurement than NEXT because it measures the total possible crosstalk from multiple pairs in the same cable, not just the crosstalk from one pair to another pair. PSNEXT is only critical in high-speed networks that transmit data over multiple pairs.

Propagation Delay

Propagation Delay tests for the time it takes for the signal to be sent from one end of a link and received by the other end.

Repeater

A repeater is a network device that repeats signals from one cable onto one or more other cables, while restoring signal timing and waveforms.

Return Loss

Return Loss is the difference between the power of a transmitted signal and the power of the signal reflections caused by variations in link and channel impedance.

RJ-11 Jack/Connector

An RJ-11 connector is the small, modular plug used for most analog telephones. It has six pin slots in the head, but usually only two or four of them are used.

RJ-45 Jack/Connector

An RJ-45 connector is similar in appearance to a modular RJ-11 connector, but is wider and has eight-pin slot positions instead of six. RJ-45 connectors are used to connect ISDN S/T Interfaces and for 10-Base-T, 100Base-T, or 1000Base-T Ethernet cabling.

Shannon’s Law

An arithmetic proof that defines the maximum data rate an analog device can achieve when sending information over a sampled, analog-to-digital connection when the analog device has no control over the timing of each individual sample. For the North American telephone system, which has a sample rate of 8,000 samples per second with a range of up to 128 sample values, Shannon’s Law shows the maximum data rate that can be achieved over voice grade lines to be about 36Kbps.

Switcher

A control which permits the selection of one image from any of several cameras to be fed into the television display or recording system.

Threshold

The minimum level at which a signal of any kind can be detected, either by the human senses or by using any electronic instrument.

TIA-568B Standard

Published in 2001, the TIA-568B standard sets minimum requirements for the various categories of cabling. The 568 "standard" is not to be confused with 568A or 568B wiring schemes, which are themselves part of the standard.

Token

The character sequence or frame, passed in sequence from node to node, to indicate that the node controlling it has the right to transmit for a given amount of time.

Token Ring

Developed by IBM, this 4 or 16 Mbps network uses a ring topology and a token-passing access method.

Trunking

Transporting signals from one point (an antenna site for instance) to another point (such as a headend), usually without serving customers directly. Trunking can be accomplished using coaxial cable, fiber optics or microwave radio.

Universal Serial Bus (USB)

A plug-n-play standard for connecting multiple (up to 127) input/output devices to a single high-bandwidth port. The design of the bus allows hot-swapping of the devices (disconnection and reconnection without powering the computer off) and automatic configuration. The USB peripheral bus standard was developed by Compaq, IBM, DEC, Intel, Microsoft, NEC, and Northern Telecom. The original version of USB (USB1.1) supports a data rate of 12Mbps, while the second version (USB2.0) supports a data rate of 480 Mbps.

Upconverter

A device used to add a lower frequency to a microwave frequency.

Uplink

The return signal from the user to the base station.

UTP

Used primarily for data transmission in local area networks (LANs), UTP network cable is a 4-pair, 100-ohm cable that consists of 4 unshielded twisted pairs surrounded by an outer jacket. Each pair is wound together for the purposes of canceling out noise that can interfere with the signal. UTP cabling systems are the most commonly deployed cable type in the U.S.