In telephony, an Automatic Call Distributor (ACD) is a device or system that distributes incoming calls to a specific group of terminals that agents use. It is often part of a computer telephony integration (CTI) system. ACD systems are often found in offices that handle large volumes of incoming phone calls from callers who have no specific need to talk to a certain person, but want to talk to a person who is ready to serve at the earliest opportunity. Routing incoming calls is the task of the ACD system. The system consists of hardware for the terminals and switches, phone lines, and software for the routing strategy. The routing strategy is a rule based set of instructions that tells the ACD how calls are handled inside the system.

Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional analogue modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call. A splitter - or microfilter - allows a single telephone connection to be used for both ADSL service and voice calls at the same time. Because phone lines vary in quality and were not originally engineered with ADSL in mind, it can generally only be used over short distances, typically less than 3mi (5 km).

See also: DSL

This takes the sound vibrations of our voices and turns them into electrical vibrations before they are transmitted over traditional telephone lines.

Auto Attendant
An automated attendant (also auto attendant, auto-attendant, or AA) system allows callers to be automatically transferred to a user's extension without the intervention of a receptionist. A receptionist, who acts as the telephone operator, can be reached by pressing 0 on most systems. Although an automated attendant is usually a feature on modern PBX and key phone systems, it is possible to provide one on standard lines and phones. There is often a 'dial-by-name' directory to find user on a system. The dial-by-name directory is usually set up last name followed by first name. Once the user name is announced the caller can press # and it will automatically ring the extension, sometimes after announcing the correct extension number for the caller's future reference.

B Channel
A B Channel (bearer) is a telecommunications term which refers to the ISDN channel in which the primary data or voice communication is carried. It has a bit rate of 64 kbit/s in full duplex. The term is applied primarily in relation to the ISDN access interfaces (PRA or PRI and BRA or BRI), since deeper in the PSTN network an ISDN bearer channel is essentially indistinguishable from any other bearer channel.

See also: ISDN

The difference between the highest and the lowest frequencies of a transmission channel (path for information transmission). Identifies the amount of data that can be sent through a given channel. Measured in Hertz (Hz); higher bandwidth numbers mean higher data capacity.

Broadband is a high-speed internet connection for transmitting multiple speech, data, or video signals simultaneously. Unlike modem connections you do not have to dial up and log on each time; broadband is always switched on.

Category 3 (Cat 3)
Commonly known as Cat3, is an unshielded twisted pair (UTP) cable designed to reliably carry up to 10 Mbits per second, with a possible bandwidth of 16 MHz. Cat3 is part of a family of copper cabling standards defined by the Electronic Industries Alliance and the Telecommunications Industry Association. Category 3 was a popular cabling format in the early 90’s but fell out of popularity in favor of the very similar but higher performing Category 5 standard. Cat3 is still being used in installations of most telephone systems and standard house telephones.

Category 5 (Cat 5)
Commonly referred to as Cat5, (usually 4 pair) high performance cable that consists of twisted pair conductors, used mainly for data transmission. Note: The twisting of the pairs gives the cable a certain amount of immunity from the infiltration of unwanted interference. Category-5 UTP cabling systems are by far, the most common (compared to SCTP) in the United States. Basic cat 5 cable was designed for characteristics of up to 100 MHz. Category 5 cable is typically used for Ethernet networks running at 10 or 100 Mbps.

Category 5e (Cat 5e)
Same as Category 5, except that it is made to somewhat more stringent standards. The category 5 E standard is now officially part of the 568A standard. Category 5 E is recommended for all new installations, and was designed for transmission speeds of up to 1 gigabit per second (Gigabit Ethernet).

Category 6 (Cat 6)
Category 6 is a cable standard for Gigabit Ethernet and other network protocols that is backward compatible with the Category 5/5e and Category 3 cable standards. Cat-6 features more stringent specifications for crosstalk and system noise. The cable standard provides performance of up to 250 MHz and is suitable for 10BASE-T / 100BASE-TX and 1000BASE-T (Gigabit Ethernet). It is expected to suit the 10GBASE-T (10Gigabit Ethernet) standard, although with limitations on length if unshielded Cat 6 cable is used.

Category 6 Augmented (Cat 6A)
CAT6A, Also referred to as 10G or 10Gigabit Ethernet. A cable standard for Unshielded Twisted Pair (UTP) supporting signaling rates up to 500 MHz. Applications include 10GBase-T, ATM, 10 Gigabit Ethernet, VoIP, and applications under development.

Central Office (CO)
A central office is the physical building used to house inside plant equipment including telephone switches, which make phone calls "work" in the sense of making connections and relaying the speech information. In telecommunications, it is commonly referred to as the (CO).

Computer Telephony Integration is a technology enabling your computer to work in conjunction with your telephone. This can range from dialing from your computer screen to a full-blown integrated call center accepting incoming calls and routing them to the appropriate telephone or device. CTI systems can handle telephone calls, faxes, and email messages.

Distribution system equipment used to terminate and administer communication circuits. In a wire cross-connect, jumper wires or patch cords are used to make circuit connections. In an optical cross-connect, fiber patch cords are used. The cross-connect is located in an equipment room, riser closet, or satellite closet.

Electrical noise coupled from one pair of wires to another within a multi-pair cable.

D Channel
D channel (data) is a telecommunications term which refers to the ISDN channel in which the control and signaling information is carried. The bit rate of the D channel of a basic rate interface is 16 kbit/s, whereas it amounts to 64 kbit/s on a primary rate interface.

See also: ISDN

Demarcation Point (DMARC)
The demarcation point is the point at which the telephone company network ends and connects with the wiring at the customer premises. A demarcation point is also referred to as the demarc, DMARC, MPOE, or minimum point of entry.

See also: MPOE

DSL (Digital Subscriber Line)
DSL or xDSL, is a family of technologies that provide digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop, although in recent years, many have adopted the term, digital subscriber line as a more marketing-friendly term for the most popular version of consumer-ready DSL, ADSL. Typically, the download speed of consumer DSL services ranges from 256 kilobits per second (kbit/s) to 24,000 kbit/s, depending on DSL technology, line conditions and service level implemented. Typically, upload speed is lower than download speed for Asymmetric Digital Subscriber Line (ADSL) and equal to download speed for Symmetric Digital Subscriber Line (SDSL).

See also: ADSL, SDSL.

DSLAM (Digital Subscriber Line Access Multiplexer)
A Digital Subscriber Line Access Multiplexer (DSLAM) allows telephone lines to make faster connections to the Internet. It is a network device, located near the customer's location, that connects multiple customer Digital Subscriber Lines (DSLs) to a high-speed Internet backbone line using multiplexing techniques. By locating DSLAMs at locations remote to the telephone company central office (CO), telephone companies are now providing DSL service to consumers who previously did not live close enough for the technology to work.

Dual-tone multi-frequency (DTMF) signaling is used for telephone signaling over the line in the voice-frequency band to the call switching center. The version of DTMF used for telephone tone dialing is known by the trademarked term Touch-Tone, and is standardized by ITU-T Recommendation Q.23. Other multi-frequency systems are used for signaling internal to the telephone network.

A firewall's function within a network is similar to firewalls with fire door in building construction. In former case, it is used to prevent network intrusion to the private network. In latter case, it is intended to contain and delay structural fire from spreading to adjacent structures. Without proper configuration, a firewall can often become worthless. Standard security practices dictate a "default-deny" firewall ruleset, in which the only network connections which are allowed are the ones that have been explicitly allowed. Unfortunately, such a configuration requires detailed understanding of the network applications and endpoints required for the organization's day-to-day operation. Many businesses lack such understanding, and therefore implement a "default-allow" ruleset, in which all traffic is allowed unless it has been specifically blocked. This configuration makes inadvertent network connections and system compromise much more likely.

G.711 is the international standard for encoding telephone audio on a 64 kbps channel. It is a pulse code modulation (PCM) scheme operating at an 8 kHz sample rate, with 8 bits per sample. According to the Nyquist theorem, which states that a signal must be sampled at twice its highest frequency component, G.711 can encode frequencies between 0 and 4 kHz. Telcos can select between two different variants of G.711: A-law and mu-law. A-law is the standard for international circuits.

G.729 is mostly used in Voice over IP (VoIP) applications for its low bandwidth requirement. Standard G.729 operates at 8kbit/s, but there are extensions, which provide also 6.4 kbit/s and 11.8 kbit/s rates for marginally worse and better speech quality respectively. Also very common is G.729a which is compatible with G.729, but requires less computation. This lower complexity is not free since speech quality is marginally worsened.

Hosted Services
Hosted VOIP provides reliability, scalability and cost savings by locating your telephone switch (PBX) in a remote enterprise data center. Employees can access the system from anywhere to get messages, make calls, and do work; it is also possible to add new users, move users, and change settings remotely. This cuts down on administration time and ensures that the business owner will not have to wait for new re-wiring. Once the VoIP solution is in place, it can be administered from almost anywhere. Most hosted packages include all of the features one would expect from a more traditional phone company: messaging, forwarding, caller ID, hold, auto attendants, toll free numbers, multiple lines, voice mail, and unified messaging. The hosting provider can also provide web site hosting, server colocation, and internet access all in one package.

Intermediate distribution frame (IDF): In a central office or customer premises, a frame that (a) cross-connects the user cable media to individual user line circuits and (b) may serve as a distribution point for multipair cables from the main distribution frame (MDF) or combined distribution frame (CDF) to individual cables connected to equipment in areas remote from these frames. IDFs, as they are called in the industry, can hold devices of different types including, but not limited to, backup systems (Hard Drives or other media as self-contained or as Raid Arrays, CD-ROM, etc.), Networking (Switches, Hubs, Routers), and Connections (Fiber Optics, coaxial, category cables) and so on.

IEEE Standards
The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-e) is an international non-profit, professional organization for the advancement of technology related to electricity. It has the most members of any technical professional organization in the world, with more than 360,000 members in around 175 countries. The IEEE Standards Association (IEEE-SA) is a leading developer of global industry standards in a broad-range of industries. See

Inside Plant
In telecommunications, the term inside plant means: All the cabling and equipment installed in a telecommunications facility, including the main distribution frame (MDF) and all the equipment extending inward, such as PBX or central office equipment, MDF heat coil protectors, and grounding systems.

See also: Outside Plant, MDF, PBX

Short for Internet Service Provider, a company that provides access to the internet. For a monthly fee, they may provide a combination of services including Internet transit, domain name registration, web hosting, and colocation. The connection to the ISP could be made using variety of methods: dial-up, DSL, Broadband wireless access, Cable modem, Frame Relay, ISDN (BRI or PRI), ATM, satellite.

Internet Protocol is the computer networking protocol used on the Internet. It converts voice messages into data packets for transmission between computers, telephones and other devices.

The Integrated Services Digital Network is an international communications standard for transmitting digital voice, video and data over digital telephone lines. The signal quality is finer and the transmission rate much faster than with analogue. ISDN supports data transfer rates of 64 Kbps (64,000 bits per second). There are two types of ISDN: Basic Rate Interface (BRI) -- consists of two 64-Kbps B-channels and one D-channel for transmitting control information. Primary Rate Interface (PRI) -- consists of 23 B-channels and one D-channel (U.S.) or 30 B-channels and one D-channel (Europe). The original version of ISDN employs baseband transmission. Another version, called B-ISDN, uses broadband transmission and is able to support transmission rates of 1.5 Mbps. B-ISDN requires fiber optic cables and is not widely available.

See also: B Channel, D Channel, PRI.

Interactive voice response, or IVR, is a phone technology that allows a computer to detect voice and touch tones using a normal phone call. The IVR system can respond with pre-recorded or dynamically generated audio to further direct callers on how to proceed. IVR systems can be used to control almost any function where the interface can be broken down into a series of simple menu choices. Once the IVR system has been constructed they can generally scale well to handle large call volumes

A Local Area Network is a network connecting computers within a single home, office or building. Each computer can access data held on a central server, as well as from other computers on the LAN. Printers and email can also be shared. A popular LAN type is Ethernet.

Least Cost Rating is an agreed procedure whereby BT allows other licensed operators to route calls over their network, resulting in cheaper telephone calls for users.

Local Exchange Carrier (LEC)
Local Exchange Carrier is a regulatory term in telecommunications for the local telephone company. In the United States, wireline telephone companies are divided into two large categories: long distance (interexchange carrier, or IXCs) and local (local exchange carrier, or LECs). This structure is a result of 1984 divestiture of then regulated monopoly carrier AT&T (American Telephone and Telegraph). Local telephone companies at the time of the divestiture are also known as Incumbent Local Exchange Carriers (ILEC).

In Telephony, a Main Distribution Frame (MDF or Main Frame) is a signal distribution frame for connecting equipment (inside plant) to cables and subscriber carrier equipment (outside plant). The MDF is a termination point within the local Telephone exchange where exchange equipment and terminations of local loops are connected by jumper wires at the MDF. All cable copper pairs supplying services through user telephone lines are terminated at the MDF and distributed through the MDF to equipment within the local Exchange e.g. repeaters and DSLAM. Cables to intermediate distribution frames terminate at the MDF. Trunk cables may terminate on the same MDF or on a separate Trunk Main Distribution Frame (TMDF).

Mid-span Adapter
Midspan power adapter is a device between a network switch and a PoE device that inserts power on the cable. Sometimes called Mid-Span Power Injectors. The adapter can provide power through unused wires (known as spare pair power) or by combining power with data signals (known as phantom feed). A common mode choke is included in the power feed to prevent noise currents from flowing through the power supply connections to earth ground, helping to minimize radiated noise.

Short for Minimum Point Of Entry, the closest practical point to where the cables of a telecommunications service carrier (i.e., a phone or cable company) cross a property line or where its wiring enters a multi-unit building. The MPOE of a multi-unit building is typically 12 inches inside the building’s foundation.

See also: DMARC

A computer network is composed of multiple connected computers that communicate over a wired or wireless medium to share data and other resources. For instance, a home computer network may consist of two or more computers that share files and a printer using the network. The size and scalability of any computer network are determined both by the physical medium of communication and by the software controlling the communication.

Network Switch
A network switch is a computer networking device that connects network devices. Network switches are capable of inspecting data packets as they are received, determining the source and destination device of that packet, and forwarding it appropriately. By delivering each message only to the connected device it was intended for, a network switch conserves network bandwidth and offers generally better performance than a hub.

Network Router
A network router is a device that forwards and routes data packets along networks. It connects at least two networks, commonly two LANs or WANs or a LAN and its ISP. A router is located where one network meets another, including each point-of-presence on the Internet. Routers have two key jobs: The router ensures that information doesn't go where it's not needed. This is crucial for keeping large volumes of data from clogging the network. And the router makes sure that information does make it to the intended destination.

Network Topology
The geometric physical or electrical configuration describing a local communication network; the shape or arrangement of a system. The most common topologies are the bus, ring and star.

Outside Plant
In telecommunications, the term outside plant means: All cables, conduits, ducts, poles, towers, repeaters, repeater huts, and other equipment located between a demarcation point in a switching facility and a demarcation point in another switching center or customer premises. Note: The demarcation point may be at a distribution frame, cable head, or microwave transmitter.

A means of connecting circuits via cords and connectors that can be easily disconnected and reconnected at another point. May be accomplished by using modular cords connected between jack fields or by patch cord assemblies that plug onto connecting blocks.

Short for private branch exchange, a private telephone network used within an enterprise. Users of the PBX share a certain number of outside lines for making telephone calls external to the PBX. Most medium-sized and larger companies use a PBX because it's much less expensive than connecting an external telephone line to every telephone in the organization. In addition, it's easier to call someone within a PBX because the number you need to dial is typically just 3 or 4 digits.

Power over Ethernet (PoE)
POE technology (commonly referred to as IEEE 802.3af) describes a system to transmit electrical power (48 volts DC), along with data, to remote devices over standard twisted-pair cable in an Ethernet network. This technology is useful for powering remote IP telephones, wireless LAN access points, Network cameras, Ethernet hubs, and embedded computers where there is no electrical power outlets.

Plain Old Telephone Service. The basic service supplying standard single line telephones, telephone lines and access to the public switched network with no added features such as call waiting or forwarding.

Telephony term for the space occupied by a customer or authorized/joint user in a building(s) on continuous or contiguous property (except railroad rights of way, etc.) not separated by a public road or highway.

Premises Wiring System
The entire wiring system on the user’s premises, especially the supporting wiring that connects the communications outlets to the network inter-face jack.

The primary rate interface (PRI) is a telecommunications standard for carrying multiple DS0 voice and data transmissions between two physical locations. All data and voice channels are ISDN and operate at 64 kbit/s. North America and Japan use a T1 of 23 B channels and one D channel which corresponds to a T1 line. Europe, Australia and most of the rest of the world use the slightly higher capacity E1, which is composed of 30 B channels and one D channel. Fewer active B channels (also called user channels) can be used for a fractional T1. More channels can be used with more T1s, within certain design limits.

In telephony and with the internet, ‘Protocol’ refers to a set of rules defining the way two systems connect, transfer data and communicate with each other. For instance, the HTTP protocol defines the format for communication between web browsers and web.

The Public Switched Telephone Network refers to the worldwide telephone system that once carried exclusively analogue telephone messages over copper wires. Today the PSTN network is almost entirely digital, encompassing mobile as well as fixed telephones.

Refers to the use of an impact tool that enables installers to make efficient IDC style connections.

Quality of Service (QOS)
In IP telephony, a procedure that ensures that voice transmission over a network is given priority over data. This ensures that telephone conversations are conducted at a high sound quality. Quality of Service uses resource reservation control mechanisms to provide different priority to different users or data flows, or guarantee a certain level of performance. Quality of Service guarantees are important if the network capacity is limited.

Symmetric Digital Subscriber Line (SDSL) is a Digital Subscriber Line (DSL) variant with T1-like data rates (72 to 2320 kbit/s). It runs over one pair of copper wires, with a maximum range of about 3 kilometers. The main difference between ADSL and SDSL is that SDSL has the same upstream data rate as downstream (symmetrical), whereas ADSL always has smaller upstream bandwidth (asymmetrical). However, unlike ADSL, it can't co-exist with a conventional voice service on the same pair as it takes over the entire bandwidth. It typically falls between ADSL and T-1/E-1 in price, and is mainly targeted at small and medium businesses who may host a server on site, (ex: a Terminal Server or Virtual Private Network) who do want to use ADSL, but don't need the higher performance of a leased line.

See also: DSL

Service Loop
When a device is terminated to the wire in the communications outlet, a fair amount of “slack” should be left on the wire and wound in the box to accommodate future trimming when devices are changed out.

Session Initiation Protocol is a new internet application-layer control (signaling) protocol enabling two or more users to conduct interactive voice, video and interactive games sessions online. It can be used to create two-party, multiparty, or multicast sessions that include Internet telephone calls, multimedia distribution, and multimedia conferences. It is widely used as a signaling protocol for Voice over IP, along with H.323 and others.

SNMP (Simple Network Management Protocol)
The network management protocol used almost exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices, and to manage configurations, statistics collection, performance, and security.

Static IP
A static IP address is an IP Address that does not change every time the device is plugged in to the network. The network information is manually entered into the device configuration. A static IP address from your ISP is required for most VPN, VOIP, Video Conferencing and Remote Administration configurations. This will allow you to always have the same internet dip address.

Structured Cabling
Structured Cabling is defined as building or campus telecommunications cabling infrastructure that consists of a number of standardized smaller elements (hence structured) called subsystems. Structured cabling design and installation is governed by a set of standards that determine how to wire a data center, office or apartment building for data or voice communications, using Category 5 or Category 6 cable and modular sockets. These standards define how to lay the cabling in a star formation, such that all outlets terminate at a central patch panel, from where it can be determined exactly how these connections will be used. Each outlet can be 'patched' into a data network switch (normally also rack mounted alongside), or patched into a 'telecoms patch panel' which forms a bridge into a private branch exchange (PBX) telephone system, thus making the connection a voice port. It is normal to see different color patch cables used in the patch panel to help identify which type of connection is being carried.

The most common legacy of this system is the line rate speeds. "T1" now seems to mean any data circuit that runs at the original 1.544 Mbit/s line rate. Originally the T1 format carried 24 pulse-code modulated, time-division multiplexed speech signals each encoded in 64 kbit/s streams, leaving 8 kbit/s of framing information which facilitates the synchronization and demultiplexing at the receiver. T2 and T3 circuit channels carry multiple T1 channels multiplexed, resulting in transmission rates of 6.312 and 44.736 Mbit/s, respectively.

TCP/IP (Transmission Control Protocol/Internet Protocol)
A protocol for communication between computers, used as a standard for transmitting data over networks and as the basis for standard Internet protocols.

An Americanism for Telephone Company.

To connect a wire conductor to something, typically a piece of equipment.

TIA/EIA-568-B is a set of three telecommunications standards from the Telecommunications Industry Association, a 1988 offshoot of the EIA. The standards address commercial building cabling for telecom products and services. The three standards are formally titled ANSI/TIA/EIA-568-B.1-2001, -B.2-2001, and -B.3-2001. The TIA/EIA-568-B standards were first published in 2001. They supersede the TIA/EIA-568-A standards set, which are now obsolete. See

Tip and Ring
Tip and Ring are common terms in the telephone service industry referring to the two wires or sides of an ordinary telephone line. Tip is the ground side (positive) and Ring is the battery (negative) side of a phone circuit. The ground side is common with the telco's central office; the battery side carries -48 volts of DC voltage when in an "idle" or "on hook" state. The combination of tip and ring, then, makes up a normal phone line circuit, just as a car's battery needs both connections leads to have a complete electrical circuit. To ring the phone to alert to an incoming call, about 90 volts of 20 Hz AC current is superimposed over the DC voltage already present on the idle line.
In the early telephone years of rotary dial, tip and ring wire reversal was of little consequence. Then came DTMF or Touch Tone. Because the tone generator is electronic, tip and ring had to be in the correct order at any given phone jack in order to be able to make outgoing calls with a Touch Tone phone. If they were reversed in polarity, there would still be a dial tone and calls could be received, but not dialed out. In most phones manufactured in the late 20th century, a diode bridge eliminates that problem. Today, tip and ring reversal is mostly immaterial, except for special circuits including DID (Direct Inward Dialing) trunks, T-1 lines, and ground start lines where the field side ("terminal") equipment--a company's PBX switch, for example--can only function correctly with correct tip and ring polarity.

Twisted Pair
Twisted Pair cabling is a form of wiring in which two conductors are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources, electromagnetic radiation from the UTP cable, and crosstalk between neighboring pairs.

Unified Messaging
Unified Messaging (or UM) is the integration of different streams of communication (e-mail, SMS, Fax, voice, video, etc.) into a single, or, unified 'message store', accessible from a variety of different devices. Unified messaging is a subset of a fully integrated Unified communications system. Today, UM solutions are increasingly accepted in the corporate environment. The aim of deploying UM solutions generally is to enhance and improve business processes as well as services. UM solutions targeting professional end-user customers integrate communications processes into the existing IT infrastructure, i. e. into CRM, ERP and mail systems (e. g. Microsoft Exchange, Lotus Notes, SAP, etc.)

An uninterruptible power supply (UPS), also known as an uninterruptible power source or a battery backup is a device which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available. There are two distinct types of UPS: off-line and line-interactive (also called on-line). They are especially important in telephone switch, network server and data center applications.

Unshielded Twisted Pair Cable. In contrast to FTP (Foiled Twisted Pair) and STP (Shielded Twisted Pair) cabling, UTP (Unshielded Twisted Pair) cable is not surrounded by any shielding. It is the primary wire type for telephone usage and is very common for computer networking, especially as patch cables or temporary network connections due to the high flexibility of the cables.

Voice over Internet Protocol is the technology for transmitting voice conversations over the internet or any other IP-based computer network. Benefits are cost-savings, the ease of managing just one network, and lots of new services including integrated messaging, voice emails, number portability, and phone account management via Internet.

A Virtual Private Network is a system in which users of a network can share confidential information transmitted in an encrypted form across the public internet.

A Wide Area Network is a communications network connecting computers, telephones and data lines housed across several sites, sometimes counties or even countries apart. Information can be freely shared. The internet is the greatest WAN.

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