Crosstalk - An unwanted transfer of signals between communication channels.

 

Unshielded twisted pair (UTP) - Two twisted wires that carry the data signals (one conductor carries a positive signal; one carries a negative signal). Twisting the cables reduces the effects of electromagnetic interference (EMI) and crosstalk.

 

Shielded twisted pair (STP) - Shielded twisted pair (STP) has a grounded outer copper shield around the bundle of twisted pairs or around each pair. This provides added protection against EMI.

 

Plenum space - A plenum space is a part of a building that provides a pathway for the airflow needed by heating and air conditioning systems, such as above a dropped ceiling or below a raised floor.

 

Riser space - An area that connects multiple floors where cables can be run. This area cannot be a plenum space.

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Light-emitting diode (LED) - A light-emitting diode is a two-lead semiconductor light source that emits visible light when an electric current passes through it.

 

Wavelength division multiplexing (WDM) - WDM joins several light wavelengths (colors) onto a single strand of fiber by using different wavelengths of laser light.

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Krone LSA-PLUS - A krone is an European-style telecommunications connector.

 

Building Industry Cross-Connect (BIX) - BIX is a cross-connect system. It consists of various sizes of punch down blocks, cable distribution accessories, and a punch down tool to terminate wires on the punch down block.

 

Power over Ethernet (PoE) - PoE is a technology that allows a single cable to provide both data and electrical power to devices such as wireless access points, IP cameras, and VoIP phones.

 

Pinout - When connecting two devices using twisted-pair cabling, the pinout determines which wire goes to which pin of the connector.

 

Local exchange carrier (LEC) - In the United States, LEC is a term used for a public telephone company that provides local services. LECs are sometimes called telcos.

 

Demarcation point (demarc) - The demarc is the line that marks the boundary between the telecommunications (telco) equipment and your private network or telephone system.

 

Main distribution frame (MDF) - A frame or rack that is used to interconnect and manage telecommunication wiring in a building. It functions like an old-time telephone switchboard, where operators used connecting wires to route telephone calls. MDF can also refer to the room that houses the traditional MDF along with networking patch panels.

 

Punch down block - A device that connects one group of wires to another through a system of metal pegs.

 

Patch panel - Patch panels permit circuits to be arranged and rearranged by plugging and unplugging respective patch cords on a mounted hardware assembly.

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Electromagnetic interference (EMI) - An external signal that interferes with normal network communications. Common sources of EMI include nearby generators, motors (such as elevator motors), radio transmitters, welders, transformers, and fluorescent lighting. When working with the radio frequency spectrum, this is known as radio

frequency interference (RFI).

 

Crosstalk - Interference caused by signals within twisted pairs of wires. For example, current flow on one twisted pair causing a current flow on an adjacent pair.

 

Attenuation - The loss of signal strength from one end of a cable to the other. This is also known as dB loss.

Electrical short - A situation in which an electrical signal takes a path other than the intended path. In the case of twisted pair wiring, a short means that a signal sent on one wire arrives on a different wire.

 

Open circuit - A condition that results from a cut in the wire preventing the original signal from reaching the end of the wire. An open circuit is different from a short in that the signal stops with an open circuit. Electricity cannot flow because the path is disconnected.

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Network interface card - A hardware device that connects a computer to the network medium. It is responsible for converting binary data into a format that can be sent on the network medium. A NIC is also called a network adapter.

 

Gigabit interface converter (GBIC) - A transceiver that converts electrical signals to optical signals and vice versa in fiber optic and Ethernet systems.

 

Small form-factor pluggable (SFP) - A transceiver that is similar to a GBIC but is smaller in size. An SFP is sometimes called a mini-GBIC.

 

XFP - A 10-Gigabit small form-factor pluggable transceiver that is similar to an SFP in size but is used for 10-Gigabit networking.

 

QSFP - A quad (4-channel) small form-factor compact hot-pluggable transceiver that is also used for data communication applications.

 

Media access control (MAC) - A unique identifier burned into the ROM of every Ethernet NIC. The first half of the MAC address (the first six digits) is assigned to each manufacturer. The manufacturer determines the rest of the address, assigning a unique value that identifies the host address.

 

Address Resolution Protocol (ARP) - A protocol that hosts use to discover the MAC address of a device from its IP address.

 

Reverse Address Resolution Protocol (RARP) - A protocol that hosts use to find the IP address of a host with a known MAC address.

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Hub - The central connecting point of a physical star. It uses a logical bus topology.

 

Bridge - A device that connects two (or more) media segments on the same subnet. It filters traffic between both segments based on the MAC address in the frame.

 

Switch - A multi-port bridge that performs filtering based on MAC addresses and provides additional features not found in a bridge.

 

Router - A device that connects two or more network segments or subnets.

 

Wireless access point (AP) - A hub for a wireless network. As with a hub, a message sent to any wireless host connected to the AP can be received by all other wireless hosts.

 

Firewall - A network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules.

 

Layer 3 switch - A switch capable of reading Layer 3 (network) addresses and routing packets between subnets.