A

Access Charge (Carrier-Common Line Change)   What local Phone companies charge long-distance companies to connect to the far-end local portion of call. A fee that everyone pays for every phone line to make up foe subsidies that long-distance services paid to help the less profitable local services before the divestiture of AT&T and the RBOC s (Regional Bell Operating Companies)

Access Line   The physical wire between the telephone network interface (NI) and the telephone company's central office main distribution frame. An access line is usually made up of five components: an F1 (or underground) pair, a cross-connect, an F2 (or aerial) pair, a service wire and a lightning protector.

All-Call Paging All-Call paging allows all multiline telephones to receive announcements through the telephone speaker at once. (at the same time)

ADSL (Asymmetrical Digital Subscriber Line) This service will allow telephone companies to provide video to home over twisted-pair telephone lines. Its current line format is T1 AMI (Alternate Mark Inversion), 16Kb/s to the CO, (for control to change the channel) and 1.528Mb/s to your TV. The distance that the signal can be transmitted over twisted pairs is extended by adaptive digital filtering, which helps correct attenuation and noise.

Analog   A signal having an infinite number of levels per cycle, in contrast to digital, which has only two possible levels per cycle (i.e., on or off).

Analog to Digital Conversion (Digital to Analog Converter/Analog to Digital Converter) A part of a channel bank that performs the function of encoding analog voice signals into a stream of binary digits. The analog-to-digital converter samples a caller's voice at a rate of 8000 times per second (The sample rate for a T1 channel is 8000 times per second). Each sample's voltage level is measured and converted to one of 256 possible sample levels. These levels are from the lowest, 0000000, to the highest 1111111. It has 256 levels because if you count binary from 0000000 to 1111111, you end up with 256, that is the highest number possible with 8 bits. The bits are then transmitted one after another at a high rate of speed to their destination, where the same happens in reverse.

Automated Attendant   The machine that answers the line and plays a message that says "Thank you for calling company X. To speak with a person in sales press one, to speak to a repair person press two." Advantages of auto attendants are that you can have one number advertised for multiple departments and not have a full-time person directing calls.

Automated Call Distributor (ACD) A phone systems accessory that routes incoming calls among a set of extensions to ensure they are handled efficiently. ACDs are generally used in call centers that process many incomding calls.

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B

B Channel   The "Bearer" channel of an ISDN circuit. It carries 64Kbp/s of end-user data. The other ISDN channel is referred to as the D or data channel, which is 16Kbp/s and carries phone company signaling along with other stuff that makes the ISDN circuit work. The two categories of ISDN are the BRI (Basic Rate Interface 2B channels and 1D channel) and the PRI (Primary Rate Interface 23B channels and 1D channel). Bandwidth. The difference in frequency between the top end of a channel and the bottom end. A good example of a bandwidth is sound. If you are listening to a sound, such as music, you notice the different pitches. All of these pitches or tones of sound are actually audio information that your ear can process. The sounds are actually vibrations. Bass tones vibrate at a slow rate, about 20 to 700 vibrations per second. Treble tones vibrate faster, from 3000 vibrations per second to 17000 vibrations per second. The total bandwidth (vibration range) that you are listening to is about 17,000 - 20 = 16980 vibrations per second. This is the range or bandwidth of human hearing.

BRI (Basic Rate Interface)   The small-size ISDN (Integrated Service Digital Network) line (the other size is Primary Rate Interface). It is made up of two bearer or "B" channels and one data or "D" channel. The B channels are 64Kbp/s each. With the appropriate service package from the phone company and correct terminal adapter, you ca can talk on channel B while using your computer modem on the other B channel. When your phone conversation ends and you hang up, the terminal adapter will send a message back to the phone company through the D channel that connects both B channels together for a total transmission of 128Kbp/s for your computer automatically.

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C

Call Announce With Handsfree Answerback The internal speaker at each multi-line telephone provides call-announce capability over the intercom link. Users can make a handsfree response to a call announce.

Call Forward Sends your calls to another destination.

Call Forwarding On All All Calls This feature allows a telephone user to designate another telephone in the office or the attendant telephone as the recipient of all calls normally directed to ring at a particular office. If you have enabled call forwarding when night transfer of ringing is activated, the system also forwards the night ringing assignment of the station. The system can also forward calls that have been forwarded once.

Call Forwarding – Busy/Ring-No-Answer The system can automatically forward busy or ring-no-answer calls to a different telephone.

Call Forward Outside System Sending calls to another destination outside the office.

Call Park   A PBX feature that allows a call to be placed on hold in a way that it can be picked up from any extension in the office. The way it works is: The attendant or any one else who wishes to park the call presses a park key on their telephone. The display on the phone then shows the extension that the call is parked in (park extensions are imaginary, just reference numbers). In this example, the display said "parked in 60" The person that parked the call then pages the person that they wish to pick up or receive the call over a loudspeaker "Johnny please pick up park 60" Johnny hears the page, goes to the nearest telephone set, and presses the park key then 60. He is immediately connected with the calling party that was parked by the attendant that answered the call.

Call Pick Up   The ability to answer a ringing phone that is not yours. You here a phone in the next office ringing, pick up the receiver and press the pick-up key on your telephone, then enter the extension number of the phone you wish to intercept the call from. Your phone is immediately connected with the call and you say " Hello, John Does (or name of the person's extension) line."

Call Pick-Up Group   A group of telephones that receive or "ring" when a certain number is called. An example of a pick-up group would be all of the phones on all the desks that ring simultaneously when a 1-800 hot line is called. When someone picks up the handset of any one of those ringing phones, they answer the call.

Call Transfer-Screened Screened call transfer allows a user to transfer outside calls from one telephone to another, via the intercom link, in one of two ways. If both stations have access to the line, they can simply use a common line pickup transfer, the transferred telephone merely presses the line button of the incoming call. If the other telephone does not have access toe the incoming line, transfer can still take place using the system transfer feature. For a screened transfer, a user transfers a call with a pretransfer announcement.

Call Transfer – Unscreened A user can transfer an active call without being announced. The transferred call camps-on to the other telephone where it rings and awaits an answer.

Call Waiting   A feature offered by local phone companies that allows someone that is talking on their phone line to receive another incoming call by briefly pressing the switch hook. The person knows they are getting another call because they here a short beep or click on the line. If a person does not have call waiting, the caller that is trying to reach them while they are on the phone will receive a busy signal. As opposed to ring when they have this service

Camp-on Re-route a call to another telephone even if all its lines are busy. (The caller is on hold and as soon as the receiver hangs up, the caller will be connected.)

Caller ID (Caller Identification)   Also known as ANI (Automatic Number Identification). A feature offered by local phone companies that sends the phone number (and often the name of the caller) down the phone line in a digital packet between the first and second ring. To receive the data, a subscriber that has signed up for the service needs to have a caller ID unit (also called a caller ID box) plugged into the phone line. The caller ID unit displays the name and the number of the calling party for each incoming call. Caller ID works only if the caller and the called party's phone service is fed out of a central office that has caller-ID capability. If the central office does not have caller-ID capability, then the display will read "out of area" to the called party. If the called party does not have caller service they will get a display that says, "no data sent."

CAT 3 Category 3   Twisted pair wire of 22 to 24 AWG. UTP or STP digital or data-transport media good to speeds of up to 16 MHz at 300 feet. Nominal impedance is 100W (+- 10%). Typical applications include analog telephone, 10 base-T, and T1 (on conditioned pairs).

 CAT 5 Category 5   Twisted pair wire of 22 to 24 AWG. UTP or STP, where each pair of wire within the sheath has a different number of twists per foot. Digital or data-transport media that is good to speeds of up to 100 MHz at 300 feet. Nominal impedance is 100W (+ - 10%). Typical applications include 10 base-T, 100 base-T, token ring, ATM and T1.

Central Office   A building that houses a telecommunications switching or trafficking system. Typical switching systems installed in central offices in North America are Lucent Technologies' 5ESS and Northern Telecom's DMS family of switches. There are five classes of central offices and five major parts to a central office. As a whole these parts are referred to as inside plant.

CENTREX   A service provided by local telephone companies that mimics an on-premise PBX. The customer purchases a block of telephone numbers. (eg. 555-1000 to 555-1999), then ever telephone on the customers premises is connected to the telephone company as an individual phone line. Each line is associated with one of the numbers in the customer's block. The telephone company then programs those specific lines to route calls as desired by the customer. Voice mail can also be incorporated into Centrex.

Company Directory A directory of names and extensions within the voice mail system.

Conference To connect two or more callers together on one telephone line.

CPE (Customer-Premises Equipment)   The equipment that is connected to a phone line. The exact definition is anything beyond the Standard Network-Interface, which includes wire, jacks, telephones, answering machines, and any other devices connected to the telephone line.

CPU (Central Processing Unit)   The device within a computer (or switch or other machine that performs complex tasks) that controls the transfer of individual instructions from one device connected to its bus (the data or I/O bus) to another, such as ROM, RAM, subcontrollers, decoders, and I/O ports. 2. Core Processing Unit. Some communications equipment manufactures call the card that controls a communication system (e.g., PBX) or portion of the system the CPU. This is because they include all of the RAM, subprocessors, buffers, clocking circuitry, and ROM in this part of the system.

CTI (Computer Telephone Integration) Used to describe the broad category of applications that involve connecting a phone system to a computer. CTI makes it possible for a computer to receive data from an incoming call and process it into something useful for your business. The most common example is using caller ID information to bring up the appropriate database file on a computer screen.

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D

DAC (Digital to Analog Converter)   A part of a channel bank that encodes analog voice signals into a stream of binary digits. The digital to analog converter or analog to digital converter samples a caller's voice at a rate of 8000 times per second. (The sample rate for a T1 channel is 8000 times per second.) Each samples voltage level is measured and converted to one of 256 possible sample levels. These levels are from the lowest, 00000000, to the highest, 11111111. The reason for 256 levels is because if you count binary 00000000 to 11111111 you end up with 256, the highest number possible with 8 bits. The bits are then transmitted one after another at a high rate of speed to their destination, where the same process happens in reverse.

DACS (Digital-Access Cross-Connect System)   A DACS is also called a DCS (Digital Cross-Connect System), depending on the manufacturer. A digital cross-connect system is quickly becoming a fundamental part of a local and long distance company's network. The DACS or DCS is a rack-mountable system that enables any circuit that interfaces with it to be electronically cross-connected from one path to another within the network it is connected to. Circuits that can interface with a digital cross-connect system include DS0, DS1, DS3 (or T3), STS-1, and SONET OC-1. An incoming circuit can be rerouted by simply making path changes in DACS administrative software. For a diagram of DACS/DCS

DAL (Dedicated Access Line)   A private circuit that provides a direct connection (or access) to a long-distance carrier or other communication service, like frame relay or an Internet service provider. Some DALs are a "full service circuit," which means that if you have a circuit that connects you directly to your Internet service provider, then the only bill you see for that service is from the Internet service provider. The local circuit is in the Internet service provider's name and they pay the phone bill for the entire service. You, of course, pay a single bill for the entire service. If you are going to get a direct Internet connection this is the way to go. If it ever stops working, you just call the Internet service provider and they determine where the problem is and fix it.

Data   In the communications industry, Data is anything that is transmitted or processed digitally. The only thing that is not Data anymore is a POTS (Plain Old Telephone Service) or analog line. A T1 line is a digital circuit. The channels carry voices, computer transmissions, and sometimes video in digitized data format.

Data Service Unit (DSU)   Also called a CSU/DSU (Channel Service Unit/Data Service Unit). A DSU is a hardware device that can come in many shapes and sizes. Rack-mount, shelf-mount, and stand-alone DSUs are available. A CSU/DSU has three main functions. The first function is to act as a demarcation point for a T1 (DS1) service from a local communications company. The second function is to provide line format and line-code conversion (B8ZS to AMI, SF or D4 to ESF, 135 V to 0 V) between the public network and the customer-premises equipment, if necessary. The third function is to provide maintenance or alarm services and loop-back for isolating problems with the T1 line or customer's equipment.

D Channel (Data Channel)   The name of an ISDN out-of-band signaling channel. The two kinds of D channels depend on which ISDN circuit you have. If you have a BRI (Basic Rate Interface, the D channel is 16Kb/s and controls two B (bearer) channels. If you have a PRI (Primary Rate Interface), then the D channel is 64Kb/s and controls 23 B channels. Both D channels carry the same information and perform the same functions. A BRI circuit requires one pair (two wires for transmission) and a PRI requires two pairs for a transmission

Dedicated Access   Reference to a telephone line that is usually provided by an IXC (Inter Exchange Carrier, long distance company) for exclusive dialing of long distance on their network. Sometimes the customer has the line installed themselves by a LEC (Local-Exchange Carrier) and gets billed separately for the dedicated access line and long distance service. Some dedicated-access lines are capable of dialing local calls, but their long-distance service is dedicated to a specific IXC.

Dedicated Circuit   Also called a private line. A private line is a pair of wire or (two pairs of wire for a T1) that runs from your location to a location that you want to be connected to with a dedicated high-speed data connection. Once a private line is installed, it is there all day, every day. There is no dialing on a private line because it does not go through switching circuitry, although it does get re-generated (the data signal on the channel is received and retransmitted). Dedicated lines could be on copper, which they have been in the past, but with the explosion of SONET, it is possible to put hundreds of private lines and switched lines on a pair of optical fibers.

Dedicated Line   A telephone line from the telephone company that is dedicated to one user or device. Most fax machines and modems are on dedicated lines. A dedicated line is not a trunk because a trunk is a line that everyone on PBX shares. A dedicated line can also be dedicated circuit (a private data line), but it is less common.

Delayed Ringing A programmable feature used for incoming call answer designed to wait a specific period of time before ringing at an alternate telephone.

  Dial-Up Line   A line that can be dialed into. Some dial-up lines include the POTS (Plain-Old telephone Service) to your house, ISDN, and switched 56 data circuits.

Dial-Up Modem   A modem that is intended to be used on the public switched telephone network. It is connected to a phone line and that phone line has a phone number that people can dial with their modems. These modems are most common in personal computers. Another type of modem is a short-haul modem, which doesn't dial numbers-it just extends a digital signal (e.g., to the other side of a building for a printer).

DID (Direct Inward Dialing)   A phone line that comes from the local phone company and connects to your PBX switch. A DID line has a phone number (and DNIS or virtual directory number attached to it) that is targeted to ring directly to a phone on the PBX network without going to a console operator, or anywhere else first. The PBX system usually needs specific DID trunk (incoming line) hardware to make DID lines work.

Digital   A signal that has only two possible levels per cycle, in contrast to analog, which can have an infinite number of possible levels per cycle. The great thing about a digital signal is that it can be regenerated easily. Even though it might pick up noise and RFI as it is transmitted along a wire, when it is regenerated, all the noise is cut out because the regenerating device looks for only two levels of signal to reproduce -1 and 0. Therefore, all the other stuff, such as white noise and maybe even an unwanted radio, are not regenerated.

Direct-Inward Dial (DID)   A phone line that comes from the local phone company and connects to your PBX switch. A DID line has a phone number (and DNIS or virtual directory number attached to it) that is targeted to ring directly to a phone on the PBX network without going to a console operator, or anywhere else first. The PBX system usually needs specific DID trunk (incoming line) hardware to make DID lines work.

Direct Outward Dial (DOD)   A feature of a PBX system that allows telephone stations to access outside dial tone or not access outside dial tone. If you pick up a phone on a PBX system and dial "9" for an outside dial tone, you might here a siren sound instead. If you do, that means that the particular phone you are dialing on does not have DOD enabled. In most PBX systems, even though DOD is not enabled, an emergency "911" call will go straight through. It is common to place special instructions on the phone to explain how to make an emergency call.

Distinctive Ring   A feature of a PBX system that allows telephone sets to ring differently. This is a very nice feature if you would like calls to ring differently than internal calls from co-workers. This helps a user to know if they should say "hello" or "Emergency service, may I help you?" Distinctive ringing is also used offices where phones are close in proximity to each other. When one phone rings, all the people in the office know whose phone it is by tone, pattern, and pitch of the ring.

DOD (Direct Outward Dial)   A feature of a PBX system that allows telephone stations to access outside dial tone or not access outside dial tone. If you pick up a phone on a PBX system and dial "9" for an outside dial tone, you might here a siren sound instead. If you do, that means that the particular phone you are dialing on does not have DOD enabled. In most PBX systems, even though DOD is not enabled, an emergency "911" call will go straight through. It is common to place special instructions on the phone to explain how to make an emergency call.

DS1 (Digital Service Level ) 1.544 Mb/s   Another name for a T1. The specific difference between a DS1 and a T1 is that the T1 is on copper and comes with a -135-V battery voltage, and the DS1 is a dry circuit, on copper or fiber-optic lines, with no battery voltage. Other than that, they are the same. A DS1 has a total bandwidth or transmission speed of 1.544Mb/s. The 1.544 Mb/s is divided into 24 64Kb/s channels. A DS1 (T1) is available in several different packages that offer different line formats and framing formats. The package that a customer requests from a phone company depends on what they want to use the DS1 for and what kind of equipment they have. Telecommunication customers use DS1 circuits as private lines to connect data services from one geographical place to another or to transport 24 dial lines to the premises. DS1 circuits are also used to connect directly to a long distance company for broadband WAN service. Telecommunications companies also use DS1 (they are T1 circuits within their own network) circuits to provide more telephone service where a shortage of twisted pairs is available.

DS1 circuit/line types and applications

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Ethernet   A family of LAN (Local Area Network) protocols. Ethernet is one of the oldest, communication protocols for personal computers. When a LAN is mentioned, two things should immediately come to mind. Physical topology and the protocols the LAN uses to manage communications between devices. Ethernet can be implemented in a bus or star physical topology. The alternative family of LAN protocols is the token passing type, which are configured as a ring topology. See Token Ring. In an Ethernet LAN, computers are given a means to communicate with each other called protocol. A protocol is a set of rules and instructions for communicating. Within protocols is a "logical topology." Even though a network can be connected as a star, it can still look like a bus to the communications equipment because all of the computers/devices are connected to the same wire (in the star diagram, the hub is a device that connects all the wire s together). The way Ethernet works is similar to the way people talk in a group. Instead of using wire to carry the binary coded information as Ethernet does, people use air to carry sound information. When there is a silence, then one of the persons in the group is able to speak. When the person speaks, they might say "Johnny do you know the answer to 5+5?" Even though all the people in the group here the question, they know it is for Johnny because the message was "addressed" to him. So only Johnny will respond "10." Then, imagine as Dawn and Nicki acknowledge a silence and both try to speak at the same time. This is confusing and no one understands the information. Ethernet has the same problem and it is call a collision. Collision is the disadvantage of Ethernet. Because of the possibility of collisions, (which happen very frequently), Ethernet is called a "contention based" protocol because all of the connected devices are contending for use of the network. Manufacturers have come up with new ways to avoid collisions, called CSMA/CD and CSMA/CA. Ethernet has many different types of wiring to connect devices, and many different NICs (Network Interface Cards) to select from that need to be installed in each computer or device on the network. Illustrated is a list of Ethernet protocols and the type of wiring used for each.

Ethernet Switch   An Ethernet protocol that gives each computer or device connected to the network its own channel to communicate with. In plain old Ethernet, all of the devices communicate on the same wire (channel). In switched Ethernet, the single wire is multiplexed into a variable number of channels-one for each device that is communicating. How fast each channel is depends on the number of devices communicating at any one time. Collision is eliminated in switched Ethernet, which was the largest inefficiency with the previous Ethernet protocols (CSMA/CD and CAMA/CA). The newer protocol transfers data at a much faster rate because of the newfound efficiency. Switched Ethernet requires its own special NICs (Network Interface Cards) and other hardware. It also requires its own software drivers.

External Modem   Also called a stand-alone modem. A modem that comes in its own package (case) and comes with a cable that plugs into a COM port/serial port on a computer or data device. External modems are popular for dial-up remote-access administration for PBX switches. The alternative to external modems is internal modems, which are popular in PCs and come in the form of circuit cards that plug into the PC's motherboard. Both do the same job equally well, but most computers only have two COM ports. If you use an internal modem, then you can use your two COM ports for other applications, you don't have to have another power outlet, and internal modems are usually less money.

Extension Each telephone in a phone system with a designated number.

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F

FCC (Federal Communications Commission)   An organization of the federal government that was set up by the Federal Communications Act of 1934. The FCC works in conjunction with the 50 state Public Service Commission bodies and Congress. It has the legal authority to regulate the following three areas of communications. Communications being defined as radio, video, telephone and satellite communications within the United States. 1. Regulate who is permitted to manufacture and sell telecommunications equipment and services. 2. Regulate the price of interstate long distance. 3. Determine the electrical standards for telecommunications, such as operating frequency or transmitting devices.

FCC Tariff   A ruling on a type of communications service. A tariff defines a service and the price that certain companies are allowed to charge. Tariffs usually restrict RBOCs and AT&T from being competitive by forcing them to sell service at higher prices than companies wish. If the FCC did not impose these tariffs on the communication giants, it would be impossible for new smaller companies to become established and compete. AT&T, USWest, PAC BELL, NYNEX, etc., would simply drop their rates so low that other companies would be driven out of business or be driven to being bought out by one of the larger companies.

Fiber Optic   A thin strand of tiny layers of glass that have different refractive properties. The layers of material have different refractive properties enable the thin strand to channel light through by bending the rays of light. The light travels through the core of a fiber, and is bent back toward the core when it enters the cladding. Fiber-Optic cable can be multi mode or single mode. Multi-mode fiber optic has a larger core than single mode. Single mode is better for transmitting long distances, and multi mode is better for transmitting multiple colors of light (or sending more than one signal on a single fiber). Single-mode fiber is much more widely used in telecommunications than multi-mode cable. SONET is a fiber-optic based protocol standard that uses single-mode, graded-index fiber optic.

Frame   One complete sampling and conversion cycle of a multiplexed data transmission. A frame is sometimes confused with a packet. A packet is an envelope that contains data and an address that the data is sent to. A packet contains data to be transmitted; error-correcting information for the data in the packet, an address, timing information, and other bits of data, depending on the protocol that the packet was formed under. A frame is a momentary picture of a multiplexed data transmission, containing bits of data, or samples from each channel.

Functional Signaling   Signaling of an ISDN line or other communication where the signaling of the circuit is performed in a manner that the user understands as well as the machines that make the communications work. An ISDN signal that is functional is a display reading that says " incoming call from John Doe," the ISDN could just give a ring or some other notification, but the call-signaling information bits in the ISDN circuit are actually decoded and passed on to the user.


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Ground Start Trunk   A phone line that uses a ground instead of a short (loop-start trunks use a short between tip and ring) to signal the central office for a dial tone. Some PBX telephones require the use of ground-start lines (trunks). Most newer PBX systems use lower loop-start (individual or on a T1) trunks or ISDN PRI trunks.

Group Listening The ability to use the handset and speaker at the same time.

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Hold Temporarily suspend a call.

Hub   A device used to broadcast data information over many lines. Simply stated, a hub makes a star wiring configuration look like a bus configuration to all the devices connected to it. Hubs are utilized in Ethernet networks.

Hunt Group   A number of telephone lines that are associated together by the telephone company central office or a PBX system. When a call comes into hunt group, it cycles through the group of lines until it finds one that is not busy, then it rings that phone (or extension, if it's a PBX system). 

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Idle Line Preference The user picks the telephone handset and is automatically connected to the first available telephone line.

In-Band Signaling   In telephone circuits (DS1 to be specific) signals can be sent two different ways: in band and out of band. Signals are digits that you dial, dial tone, the phone being off the hook, ringing, etc. An in-band telephone line is like the one in your home; the digits that you dial and the ringing are carried within the channel you talk on. Out-of -band signaling is a method that telephone companies and businesses use for larger PBX applications and data-transfer applications. An Out-of-band, signaled DS1 has 24 multiplexed channels. The 24th channel carries the signaling for the other 23 channels or phone lines. The advantage of out-of-band signaling is that each channel has an increased capacity to carry data (8Kb/s more) and the 23 channels are not used to find out if a line is busy (both directions, in and out). The off-hook sensing is and busy signaling is done in the 24th channel. If you have a system that gets thousands of calls per day, this can reduce traffic.

Inside Wiring (IW)   The telephone wire that is on the customers side of Telephone Network Interface. IW includes jacks and any wiring in or attached to the outside of the house, as long as it is electrically on the customer side of the network interface.  

Integrated Services Digital Network (ISDN)   ISDN is a service that first evolved in 1979. It brings the features of PBX systems and high-speed data-transfer capability to the telephone network. The only thing that makes ISDN complicated is the many available features. The two kinds of ISDN lines are Primary Rate Interface (PRI) and Basic Rate Interface (BRI). Two types of channels are contained within an ISDN circuit. The B (bearer) channel carries the customer's communications, and a D (data) channel provides control and signaling for the B channels. The BRI ISDN line has two B channels and one-D channel. A PRI has 23 B channels and one-D channel. The separate control of the ISDN line over the D channel is what enables the broad flexibility and features available with ISDN. When you are talking or sending data transmissions over an ISDN line, the voice and/or data is carried by the B channels. While you are talking on your ISDN line, you can still dial digits (signal the central office) to change or alter the state of your service because of your separate D channel. For example, imagine you want to arrange a meeting with a client. You dial the client's telephone number on your ISDN telephone to reach the client. While you are speaking with the client, you can dial up for Internet access on your computer and put two baseball tickets in at the ticket counter using the same phone line. Then you can fax your client directions by downloading a map provided by the ticket office, disconnect and redial your clients fax number. All of this occurs while you are talking to your client the entire time. Through the advanced convenience and flexibility of ISDN, you can send different types of data and messages to different places at the stroke of a few buttons, and at a much faster speed than a regular telephone line. If you are interested in ISDN, call your local phone company. They can help you decide on what type of terminal adapter (equipment that connects your computer and phone equipment to the ISDN line) to buy and what kind of features to subscribe to. ISDN is not yet available everywhere.

Intelligent Hub   A hub that has the ability to be electronically reconfigured (manually or remotely) and perform additional functions, such as protocol conversions and bridging functions.

Interconnect Agreement   This is also known as a co-location agreement. The two types of co-location agreements are physical and virtual. A physical co-location is an interconnection agreement and a physical place where telephone companies hand-off calls and services to each other. This is usually done between a CLEC and RBOC. The CLEC installs and maintains interconnection equipment usually consisting of optical carrier (SONET) equipment and a digital cross-connect system. There are other types of co-locations. Alarm companies like to have their alarm-signaling equipment located in the local central office for security and convenience of connecting alarm circuits. Long-distance companies co-locate with local telephone companies as well. A virtual co-location is an interconnection agreement and physical place where telephone companies hand off calls and services to each other. This is usually done between a CLEC and RBOC. A virtual co-location is when telephone company A (the CLEC) requests that their phone company's network be connected to telephone company B's (the RBOC's) network. Telephone company B charges company A lot of money. Company B owns, installs, and maintains the equipment. To company A, the interconnection is virtual, because they never physically do anything to it when and after it is installed. Company B likes this, because company A does not get free access to their premises.

Inter LATA (Inter Local Access Transport Area)   Simply stated, a LATA is an area code, Inter LATA refers to services that go from one area code to another, like long-distance telephone calls. Intra LATA refers to services that originate and terminate in the same area code.

Internet   A network of computers that originated as ARPANET, an information communications project of the United States Department of Defense. Over time, many other organizations, private and public have utilized the project by connecting their computers to it. Its primary protocol is TCP/IP. Today, many Internet service providers can offer access to the Internet for as little as $15 per month. The Internet is growing exponentially as more service providers and customers gain access to it. It currently links millions of computers, with which user find and exchange information, buy and sell services or products, and play games.

Internet Server   A server that users access for Internet services. Popular Internet services include access to the Internet, e-mail, news updates of the subscribers choice, web pages, etc. An Internet Server is owned by an Internet service provider.

Internet Service Provider (ISP)   An Internet service provider purchases direct access to the Internet through an Internet company, such as UUnet and resells the service to smaller subscribers via dial-up modem (or to large customers via frame relay or private line T1). The ISP adds other services of their own, such as e-mail, news updates of the subscribers choice, web pages, etc.

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K

Key Telephone Systems   The less expensive and less flexible to a PBX system. On a key system, each telephone line appears under a key (button) on the phone. To access an outside line or answer an incoming call, you press the key associated with that line. Key systems are digital and have six major parts, the KSU (Key Service Unit), line interface, station interface, power supply, connectivity, and the key sets (telephone sets). Most key sets are user friendly, and can be installed by a user that knows little bout telephony. The KSU is the cabinet that contains the electronics that controls the switching between key sets and phone lines. Some key systems have detachable line and station interfaces that plug into the KSU. The system usually comes with a specific number of incoming line interfaces (6) and a specific number of station interfaces (16). This size system is commonly referred to as a 4-16 (four/sixteen). The power supply is often a "power-adapter" type. Some manufacturers offer a UPS back-up option specially designed for the key system. The key-set telephones are sold individually, in a variety of choices that include 20-key (10 button), 20-key (20 button), display, and hands-free.


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L

Line Groups Group outside lines together in up to four different groups. Grouping reserves certain lines for certain clusters of telephones (need to reword this one).

Lines – Trunks, CO – Central Office Lines Connections to the outside phone network. The number of lines is the sum of incoming and outgoing calls that can occur simultaneously.

Last Number Redial – Automatically redials the last external telephone number that you dialed.

LAN (Local Area Network)   A group of computers connected together within a building or campus. LANs are the most detailed of computer networks because they deal with the applications and operating systems of computers. The distinguishing thing about LANs is the way that the computers are connected and the protocol at which they communicate over the media that connects them. The two major LAN protocols (logical topologies) are Ethernet (star and bus) and Token Ring. Both Ethernet and Token Ring have evolved into switched Ethernet and switched Token Ring, which are different in operation and speed than their predecessors. Large LANs use an operating system to control the LAN environment, such as Novell or Windows NT. Another component of LANs is the server, which can either run programs or store data for computers connected to the network. Servers are simply other computers (usually with more processing power and memory) that are configured by an operating system by an operating system, such as Novell and Windows NT, to perform a specific function.

LATA (Local-Access Transport Area)   Simply stated, a LATA is an area code, Inter LATA refers to services that go from one area code to another, like long-distance telephone calls. Intra LATA refers to services that originate and terminate in the same area code.

LCD (Liquid Crystal Display)   LCDs are electronic display devices that operate by polarizing light so that a nonactivated segment appears invisible against a background. An activated segment does not reflect light (absorbs it) and therefore appears darker than the background. TTL is not generally used to drive LCD displays because it does not completely "deactivate the segment". A few tenths of a volt are present-even when a TTL logic device is completely in the "off" state. CMOS is the best type of device for driving LCD displays because of its ability to turn completely off and have no remaining bias voltage. LCD displays consume very little power, in contrast to other display methods (CRT, LED), but are sensitive to heat and need external light to be viewed in the dark. LCD displays consume little space compared to CRTs and are used in laptop computers.

LD (Long Distance)   An abbreviation commonly used in PBX and key-system operator manuals.

LEC (Local Exchange Carrier)   Most commonly a reference to one of the seven BROCs. A telephone company that provides telecommunications services to end-users and bills them for it. A local exchange carrier has switching networks and outside plant or cellular service to serve its customers. Examples of local -exchange carriers are: NYNEX, USWest, GTE, PAC BELL, Southern Bell Telephone, and a myriad of cellular-telephone service providers. The newest breeds of local exchange carriers are CLECs (Competitive Local Exchange Carriers). They have all the same services s the RBOCs, except that they are generally only located in large metropolitan areas. Some larger CLECs include TCG (Teleport Communications Group), ELI, (Electric Lightwave Inc.), Brooks Communications, and MFS (Metropolitan Fiber Systems). CLECs use (almost exclusively) SONET in conjunction with DCS as the foundation of their network architecture.

Load Coil   A load coil is a voice-amplifying device for twisted-pair wire. A load coil is usually placed on each twisted pair for a voice line every 3000 feet past a central office. Coils are usually located in vaults, with twisted-pair splices. A typical load coil has an inductance of 30 mH. Other coils, used for other applications are usually referred to as choke coils.

Local-Access Transport Area (LATA)   Simply stated, a LATA is an area code, Inter LATA refers to services that go from one area code to another, like long-distance telephone calls. Intra LATA refers to services that originate and terminate in the same area code.

Local Central Office (LSO)   Local serving office. A central office that performs telecommunications switching for a specific number-plan area. The number-plan area is currently defined by the first three digits of a seven-digit telephone number. When number portability takes effect, a local central office will no longer be defined as its number-plan area. It will be defined by the laws set forth by the PUC the area its outside plant reaches. Typical switching systems installed in central offices in North America are Lucent Technologies' 5ESS and Northern Telecom's DMS family of switches. There are five classes of central offices and a local central office is a class five. There are five major parts to a central office. As a whole the parts are referred to as inside plant.

Local Exchange   A reference to the serving area of a central office. Until number portability takes effect, the first three digits of your seven-digit telephone number defines the exchange (specific central office) you are located in. After number portability takes effect, an exchange will be defined as the tariffs and laws set forth by the local governing PUC. Your telephone number will be associated to you, rather than a central-office equipment port or address. You and your phone number will be tracked in a national database that allows you to take your phone number anywhere you move to, or any phone company you switch to, within an area code. Eventually, you will even be able to transfer your number to a cellular or PCS phone.

Local Exchange Carrier (LEC)   Most commonly, a reference to one of the seven RBOCs. A telephone company that provides telecommunications services to end-users and bills them for it. A local exchange carrier has switching networks and outside plant or cellular service to serve its customers. Examples of local -exchange carriers are: NYNEX, USWest, GTE, PAC BELL, Southern Bell Telephone, and a myriad of cellular-telephone service providers. The newest breeds of local exchange carriers are CLECs (Competitive Local Exchange Carriers). They have all the same services s the RBOCs, except that they are generally only located in large metropolitan areas. Some larger CLECs include TCG (Teleport Communications Group), ELI, (Electric Lightwave Inc.), Brooks Communications, and MFS (Metropolitan Fiber Systems). CLECs use (almost exclusively) SONET in conjunction with DCS as the foundation of their network architecture.

Local Loop   The pair of wires that extends from the local telephone company's central-office main-distribution frame to the customer's premises.

Loop-Start Trunk   A trunk is a line that comes from a central office. The type of trunk determines which type of signaling the line requires to work. A loop-start trunk is a two-wire central-office trunk or dial tone line that recognizes an "off hook" situation when a telephone switch hook puts a 1000-ohm short across the tip and ring when the handset is lifted. This is the most common type of line. It is also called a POTS line and Plain Service Line. Other types of trunks are ground start, and E&M trunks, ISDN PRI, and ISDN BRI.

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M

Mbps (Megabits Per Second)   Equivalent to one million bit per second. Memory or data transferred per unit of time is measured in bits. Memory storage is measured in bytes. The difference in abbreviation is that bits are lower case (b) and bytes are upper case (B)

Measured Rate Service   Abbreviated 1MR for residential and 1MB for business, this type of telephone service is offered by local telephone companies. Measured-rate service means that a line is billed on a "per call basis." Telephone companies in the Southern and Western United States have tried to abolish measured service by encouraging customers to subscribe to flat-rate services, abbreviated 1FR for residential and 1FB for business use.

Multiplex   Multiplexing is the process of encoding two or more digital signals or channels on to one. Channels are multiplexed together to save money. When we use all of the wires in a cable and need more, it costs less to add electronics on the ends of a cable than to install a new one (imagine the expense calling NY to LA). A T1 encodes 24 channels into 1 by using frequency division multiplexing. In a simpler explanation, a T1 makes it possible to place 24 lines that once needed 24 pairs on only 2 pairs. When a group of signals are multiplexed together, they are all sampled at a high rate of speed, faster than the combined speed of all the channels being multiplexed.

Mux   A shortened name for multiplexer.

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Network Interface (NI)   Also called a Standard Network Interface (SNI), demarcation point, or lightning protector. The device that contains carbons to protect a phone line from being overloaded by lightning and acts as the separation point between the telephone company's wire and the customer's wire, which is also called the IW (Inside Wire).

Night Ringing Night ringing is an attendant-controlled feature that transfers the day ringing program of all incoming calls to a particular telephone(s) for off-hour or special purpose answering.

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OC-1 (Optical Carrier 1)   The beginning of the SONET-level transmission speeds. An OC-1 is capable of carrying one DS-3 within its payload. Its transmission carrier speed is 51.840Mb/s. OC-1 can be converted into an electrical signal, which is called an STS-1 (Synchronous Transport Signal-1).

OC-3 (Optical Carrier 3)   A SONET level transmission speed. It is capable of transporting three DS-3 signals, which is equal to 155.520 Mb/s.

OC-12 (Optical Carrier 12)   A SONET level transmission speed. It is capable of transporting three DS-3 signals, which is equal to 622.080 Mb/s.

OC-48 (Optical Carrier 48)   A SONET level transmission speed. It is capable of transporting three DS-3 signals, which is equal to 2.488 Gb/s.

OC-192 (Optical Carrier 192)   A SONET level transmission speed. It is capable of transporting three DS-3 signals, which is equal to 90953 Gb/s.

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Prime Line Automatic A particular telephone line can be programmed so that when you pickup the handset that line is the one you access at that time – outside line, intercom line.

POTS (Plain Old Telephone Service)   A telephone line, with a telephone number, like the standard ones subscribed to by residence and many small businesses.

PRI (Primary Rate Interface)   One of the two ISDN (Integrated Services Digital Network) circuit sizes. ISDN first evolved in 1979. It brings the features of PBX systems and high-speed data-transfer capability to the telephone network. The only thing that makes ISDN complicated is the many available features. The two kinds of ISDN lines are Primary Rate Interface (PRI) and Basic Rate Interface (BRI). Two types of channels are contained within an ISDN circuit. The B (bearer) channel carries the customer's communications, and a D (data) channel provides control and signaling for the B channels. The BRI ISDN line has two B channels and one-D channel. A PRI has 23 B channels and one-D channel. The separate control of the ISDN line over the D channel is what enables the broad flexibility and features available with ISDN. When you are talking or sending data transmissions over an ISDN line, the voice and/or data is carried by the B channels. While you are talking on your ISDN line, you can still dial digits (signal the central office) to change or alter the state of your service because of your separate D channel. For example, imagine you want to arrange a meeting with a client. You dial the client's telephone number on your ISDN telephone to reach the client. While you are speaking with the client, you can dial up for Internet access on your computer and put two baseball tickets in at the ticket counter using the same phone line. Then you can fax your client directions by downloading a map provided by the ticket office, disconnect and redial your clients fax number. All of this occurs while you are talking to your client the entire time. Through the advanced convenience and flexibility of ISDN, you can send different types of data and messages to different places at the stroke of a few buttons, and at a much faster speed than a regular telephone line. If you are interested in ISDN, call your local phone company. They can help you decide on what type of terminal adapter (equipment that connects your computer and phone equipment to the ISDN line) to buy and what kind of features to subscribe to. ISDN is not yet available everywhere.

Private Branch Exchange (PBX)   A telephone system used to maximize use of telecommunications services purchased from a telecommunications company. A PBX simply takes telephone lines from the outside world and makes them accessible to extensions within a certain building, home or office. PBX systems are available in many sizes, with many software and feature options. PBX features include call forwarding, speed dial, internal/external paging, and call detail recording (call accounting). The larger PBX manufacturers are AT&T, Northern Telecom, Siemons, Toshiba, Iwatsu, NEC, and Rolm. PBX systems have six main parts: the cabinet-backplane (also called a KSU, Key Service Unit), the station/telephone connectivity, the trunk/telco connectivity, the power supply, the telephone/extensions, and the administrative access.

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R

Ringing Line Preference Each telephone can be programmed that when you lift the handset is answers a particular telephone line over another.

RBOC (Regional Bell Operating Company)   At the time of divestiture, there were 22 BOCs, grouped into seven Regional Bell Operating Companies (RBOCs). For a listing of the BOCs and RBOCs, see Regional Bell Operating Companies.

Redundancy   To have one main and one back-up. SONET equipment is capable of being configured in a redundant manner, with two fiber-optic routes (in a ring) and duplicates of the electronic cards that control the communications transmission. Many PBX systems are capable of being configured with redundant CPU and memory cards. The idea behind redundancy is that if one device fails, the other will take over, without a loss of service.

Regional Bell Operating Company (RBOC) Telephone Company RBOCs:   SBC/Ameritech, Bell Atlantic, Bell South, NYNEX, Pacific Telesis, Southwestern Bell, Qwest

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S 

SONET (Synchronous Optical Network)   SONET is strictly a broadband transport system. It is implemented over fiber optic and is able to be configured in a ring, which allows it to reroute traffic with no interruption of service if a fiber is cut. CLECs are implementing SONET as the mainstay of their network construction. SONET is based on a hierarchy of STS (Synchronous Transport Signals), which is the electrical version of an OC-1 (Optical Carrier Level-1). An OC-1 has a transmission speed of 51.84 Mb/s. SONET works similar to switched token ring, except at much higher speed. SONET permits a virtual tributary to be created from one node to another on a network. Virtual tributaries can be equal to a DS1, DS3, STS-1 or any of the OC levels. The important thing to know about a SONET network is that it simply replaces the older telecommunications technology copper twisted-pair outside plant with fiber optic and electronics.

Station Speed Dial Program into your telephone set numbers that you dial frequently. Pick up the handset, press the preset speed dial button, the line is ringing.

System Speed Dial Speed dials can be set up through the system to be the same on everyone's individual telephone.

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T1   A T1 is a standard 1.544Mb/s carrier system used to transport 24 telephone lines or various broadband services from one point to another (also called a DS1, but a DS1 is the service given to a customer without the -135-V carrier). T1 is the standard carrier for the United States, Canada, Japan and Singapore. All other countries use the E1 standard (30 channels on four wires). The T1 is a four-wire circuit, two wires for transport and two wires for receive. The T1 line voltage is -135 V. The T1 circuit can carry voice or data, Its use determines the variables of T1 service, framing format, and line format. See also DS1.

Tariff   A pricing structure of telecommunications services that is offered by a communications services company and accepted by the Public utilities Commission (PUC).

TCP (Transmission Control Protocol)   A data packet protocol (rules for communications between devices) for data exchange between computers, printers, servers or anything else that is capable of being loaded with the protocol driver. The protocol driver can be loaded in software or embedded in hardware (PROM). It was developed by ARPA/DARPA (Advanced research Projects Agency/Defense Advanced research Projects Agency) of the U.S Federal Government.

TCP/IP (Transmission Control Protocol/Internet Protocol)  It was initially called TCP, but it became the standard for the Internet, and the "/IP" was added to the end. See TCP.

Terminal Adapter   A device that converts an ISDN line into regular POT service so you can connect a standard telephone and/or modem to an ISDN line.

Trunks Also known as lines, these are connections to the outside phone network. The number of trunks determines the number of incoming and outgoing calls that can simultaneously occur.

Transfer Send a call to another telephone within your system/office, or to an external telephone.

T Interface   An ISDN-compatible digital interface. For example, a T interface fits between an ISDN telephone and an ISDN line. 

Trunk   A trunk is a line that comes from a central office. The type of trunk determines which type of signaling the line requires to work. A loop-start trunk is a two-wire central-office trunk or dial-tone line that recognizes an "off hook" situation when a telephone switch hook puts a 1000-W short across tip and ring when the handset is lifted. This is the most common type of line. It is also called a POTS line or plain-service line. Other types of trunks are ground start and E&M trunks (Ear and Mouth), T1 with in-band signaling, ISDN PRI, and ISDN BRI.

Trunk Group   A group of telephone lines that connect a PBX (Private Branch Exchange) or key telephone system to the phone company, and are used for specific applications, such as incoming customer-service lines, sales lines, or information lines. A specific group of trunks can also be configured for outgoing calls only.

Twisted Pair   Communications wiring consists of 19 to 26 AWG solid and insulated wires. Twisted-pair wire consists of "pairs" of color-coded wires. Common sizes of twisted-pair wire are 2 pair, 3 pair, 4 pair, 25 pair 50 pair, and 100 pair. Twisted-pair wire is commonly used for telephone and computer networks. It comes in Ratings of CAT3 (for voice), CAT4 (voice and 10-base-T), and CAT 5 (for 100-base-T and token ring). 


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Unanswered Call Transfer A transferred cal that goes unanswered after predetermined length of time will return to the original telephone that transferred it.

UPS (Uninteruptable Power Supply)   A battery back-up system. When the power goes out, the UPS converts the DC battery power to AC power to run the system.

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Voice Call Make a voice announcement of begin a conversation through the speaker of another telephone without first making the other telephone ring (without dialing that extension).

Voice Mail   An answering machine system that integrates with a PBX (Private Branch Exchange) or key telephone system. Octel (now a part of Lucent technologies) is a manufacturer of voice-mail systems that are used in business-office applications and in central-office applications for telephone companies to offer voice mail/voice messaging as a service to subscribers. Vice mail can also be purchased as a network interface card with software that runs on a PC.

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Wide Band   Another name for Broadband. Incorporating more than one channel into a communications transmission. T1 is a broadband communications protocol because it carries 24 conversions over four wires. Cable TV is also broadband because it carries many TV channels over one coax.

Wireless LAN   A local-area network of computers and peripheral devices that communicates via radio signals or light waves (low-power laser beams). These systems are useful in situations where the cost of installing wiring between the devices is very expensive or for temporary/ mobile applications.

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