Glossary of Telecommunications Terms
by Ed Mass
Access
A generic term that refers to the physical lines, typically copper and sometimes fiber, that connect a customer’s location to a local telephone services company to carry the communications traffic.

ATM
Asynchronous Transfer Mode. A service that was designed to carry voice, data, and video traffic. Most services developed from a specific need to carry only one type of traffic. ATM is a scalable service, meaning it can carry traffic up to very high speeds. ATM is growing in use for the backbone infrastructures of many telecommunications carriers and large corporations. Over time it will become economical for businesses of all sizes.

Cellular
Analog cellular (the original type of cellular service) and newer, digital cellular services. Digital cellular offers greater security, quicker connections, clearer sound, and the potential for a greater variety of enhanced services. Cellular services are all based on erecting towers in a geographic area to conduct wireless signals between mobile phones and the physical lines that connect to the local telephone system.

CLEC
Competitive Local Exchange Carrier. This is the general term used for any company that offers local telephone service and was not the original monopoly telephone company in a specific area.

CLEC Facilities Based
Refers to a CLEC that owns or leases either or both of the lines or switches that carry traffic. This type of CLEC has more control over its costs and its ability to offer new services.

CLEC Resale
Refers to a CLEC that does not own or lease either the lines or switches that carry traffic. A resale CLEC simply buys local phone services from the Incumbent Local Exchange Carrier at wholesale rates and sells them at retail rates.

Dedicated Long Distance Services
A direct line between an organization’s location and a long distance carrier’s switch. If the line is leased from a Local Exchange Carrier then a monthly lease fee is paid to the LEC for the use of the line. Since the direct line bypasses the LEC’s switches, no per minute fees are paid to the LEC. Therefore, per minute long distance rates are lower than switched long distance rates. (See also Switched Long Distance Services.)

Enhanced Services
Such as caller ID, call waiting, three-way calling, and many more that are currently available. Digital technology allows a greater capability to create new services faster, more easily, and more economically than could be accomplished with analog technology.

Facilities
Refers to the physical infrastructure of switches and lines to carry communications traffic.

Frame Relay
A type of service that originated to carry data communications traffic. Although technology has developed to allow it to also carry voice traffic its justification is first based on the need to carry data traffic. Only after being justified for data is it then looked at for voice as an add-on service.

ILEC
Incumbent Local Exchange Carrier. This refers to the original monopoly telephone company in a specific geographic area.

IP Telephony (also see VOIP)
IP Telephony uses IP (Internet Protocol) technologies to carry voice traffic. Voice traffic is carried over your data network using IP technologies that carry your data. This has the following advantages:

Using one cabling infrastructure to carry both data and voice traffic instead of separate cabling infrastructure for each. This can have significant cost savings especially if you are moving your office or setting up a new office.
Easier maintenance of your phone system through a GUI (graphical user interface). You can perform changes to your system that previously required you to have your telephone equipment vendor perform. Therefore, you can significantly reduce your maintenance costs.
Easier moves of telephone sets. When moving from one location in your building to another, it previously required re-programming the telephone switch and physically changing some wires in the “telephone closet.” With IP Telephony as you pack up your desk supplies and plants, you also grab your telephone and simply plug it into the ethernet connection in your new location. All your personal settings move with you. Costs for moves are dramatically reduced.
Connecting remote sites on your private network, or even over the public Internet, is relatively easy and much less costly.
Software upgrades are much easier and can be performed by you instead of paying the telephone equipment vendor to do them.
There are many other benefits to IP Telephony but hopefully this brief overview is enough to peak your interest to look into it at the right time. You don’t need to make a total swap out of your current phone system. It is possible to gradually introduce it into your organization and interface it to legacy systems.
There are some key issues to consider to implement IP Telephony such as the capabilities and programming of your switches and routers. You should also review the load on your network. Where data can accommodate delays in delivery of packets and users won’t notice this, voice traffic cannot tolerate much delay otherwise the voice quality will suffer. There are standards for QOS (Quality of Service) that allow switches and routers to give priority to voice traffic. These need to be properly implemented.
ISDN
PRI and BRI. PRI is Primary Rate Interface which allows 23 channels of any type of traffic plus one channel that carries signaling information. Signaling information consists of routing data to determine where the call is coming from and going to and what to do with it. This is often used instead of T-1 service as more carriers are able to offer ISDN service.

IXC
Interexchange Carrier, also known as a "long distance company." A generic term that refers to a company that carries long distance calls as opposed to local telephone calls.

LEC
Local Exchange Carrier. A generic term that refers to the ILEC (since there was only one monopoly company in any given area) and now refers to either an ILEC or a CLEC.

PBX
Stands for Private Branch Exchange and refers to the telephone switch (see switch) within the premises of an individual organization.

Private Line
A service where a line is leased at a monthly rate between two locations. The locations can be anywhere, local or long distance. It is often used to carry data traffic directly between two locations.

PSC or PUC
Public Service Commission or Public Utility Commission. The state regulatory agency that approves the services and rates of all utilities including telephone services. In Missouri our regulatory agency is called a PSC.

Switch
Refers to a telephone switch that moves the communications traffic between different end points. The end points could be two telephones within the same office or they could be two telephones across the world where the communications traffic goes through a series of connected switches from different LECs (local telephone companies) and IXCs (long distance telephone companies).

Switched Long Distance Services
Long distance services offered on lines where there is not a direct connection between a LEC and an IXC. Since these lines can be used for local calling, the long distance calls had to be "switched", or transferred, to the IXC. Therefore, the LEC charges the IXC a fee to do the switching, or transferring, of the calling. As LECs offer both local and long distance calling, the distinctions between switched and dedicated long distance services will disappear.(See Dedicated Long Distance Services.)

T-1
A digital technology that allows 24 channels of conversation to occur over just two pair of wires. Analog technology requires a pair of wires for a single conversation. Digital technology can be used to carry voice, data, and video traffic more easily and at faster rates than analog technology.

Traffic
A generic term for any type of communications information that must be conveyed between two locations, e.g. voice, data, and video. This is the equivalent to vehicle traffic on a highway. The "vehicles" are voice, data, and video traffic in the communications world. The "streets and highways" are the lines, copper and fiber, that carry the communications traffic. Highways carry more vehicles at faster speeds than streets. Fiber lines carry more communications traffic at faster rates than copper lines. The "stop lights" that allow traffic to change from one direction to another are the switches in the communications world. Only the switches have much greater "intelligence" than the street lights. The switches don’t just start and stop traffic. They decide how the traffic should be routed for different types of traffic that come into and go out of the switch.

VOIP (Voice Over Internet Protocol) (also see IP Telephony)
VOIP is used to refer to IP Telephony as described above. It is also used to refer to using the public Internet to carry voice traffic. When the public Internet is used, you (the user) don’t have the same control over the Quality of Service as you do over your own network. Therefore, it is possible for voice quality to suffer although with today’s technologies it can often be very good.

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