How A Phone Call Really Works
Routing On A Switched 1+ (Outbound) Voice Call

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Definitions For Terms On This Page
Access Lines
Carrier
Carrier Identification Code (CIC)
Competitive Access Provider (CAP)
Competitive Local Exchange Carrier (CLEC)
Facilities
Interexchange
Local Exchange Carrier (LEC)
Local Loop
PBX (Private Branch Exchange)
POP (Point of Presence)
Switch
Switched Service

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Access Lines - Bet you didn't know it, but there's actually a very important link in between the local telephone company's switch and the long distance carrier's network. It's called "Access Lines." When a local telephone company routes your call to your chosen long distance carrier, the call passes over interim facilities known as "Access Lines" to reach the long distance carrier's network at their Point of Presence (POP). Same thing happens in reverse when the call reaches the end of the line. To get your call off the long distance network, the call must first travel through the long distance carrier's POP at the receiving end, then over their "Access Lines" lines to the local telephone company's switch to be directed to the called party's phone. [Back to Diagram]

Carrier - A long distance telephone company which uses it's own transmission facilities and network lines for the majority of it's customer's calls. Many people refer to any long distance company as a carrier, even if it does not own or operate it own transmission facilities or network. Your local telephone company identifies each long distance Carrier by a unique Carrier Identification Code (CIC). [Back to Diagram]

Carrier Identification Code (CIC) - A 4-digit code (3-digits prior to 7/1/98) used by the local telephone company to identify a long distance carrier. Each long distance carrier is identified by a unique 4-digit CIC (3-digits prior to 7/1/98). When a call is placed the CIC tells your local telephone company which long distance carrier to route your call over. Click here for details on the "10-XXX" (5-digits) dialing convention recently changed to "1010-XXX" (7-digits) by order of the FCC effective 7/1/98.

Most Lightyear services are Flat Rated, click here for more information about 1+ Services. [Back to Diagram]

Competitive Access Provider (CAP) and Competitive Local Exchange Carrier (CLEC) - Companies that compete with the local telephone company (LEC). Most CAP's and CLEC's were created around the time the Telecommunications Reform Act of 1996 opened up local telephone services to competition. Prior to the 1996 Act, the LEC's generally had a monopoly on providing local exchange services (dial tone, hunt groups, local loops, etc.) [Back to Diagram]

Facilities - Typically refers to transmission switches and equipment used by long distance carriers to handle a long distance call. [Back to Diagram]

Interexchange - The part of long distance voice and/or data transmission carried over the long distance carrier's facilities. [Back to Diagram]

Local Exchange Carrier (LEC) - Your Local Telephone company. [Back to Diagram]

Local Loop - When you pick up the phone you hear a dial tone. That sound comes from an electronic switching device located at your local telephone company "central office," and is carried to your phone via copper wires called "twisted pair." The wires "loop" from the switch to your telephone, hence the term "local loop." When you dial a long distance number, the call travels out the loop to the central office, and from there down the loop connecting to the called party. [Back to Diagram]

PBX (Private Branch Exchange) - A private phone system (switch) used by medium and large companies, connected to the customer's local telephone company (LEC). Performs a variety of in-house routing and switching. [Back to Diagram]

POP (Point of Presence) - 1) Physical place where a long distance carrier interfaces with the network of the local telephone company (LEC). 2) The point at which the local telephone company terminates customer's circuits for long distance calls or leased line communications. [Back to Diagram]

Switch - Guess we ought to explain what this is, even though it's not technically a "part" of a telephone call. Rather a switch is a device that handles calls. When a long distance number is dialed, the switch identifies the number you are calling from and routes the call to your long distance carrier (as identified at the local telephone company by your long distance carrier's Carrier Identification Code (CIC)) through their access lines and POP. [Back to Diagram]

Switched Service - All residential and most businesses use this type of telephone access. It refers to the connection between your phone and the long distance companies' switch at their POP when you make a long distance telephone call over standard phone lines. This connection is made by a local telephone company (LEC) whose equipment switches many calls to and from callers using the telephone company's common wiring and switching equipment, hence the term "switched service". Long distance rates for switched calls are generally more expensive that rates for dedicated calls because the local telephone company actually switches every switched call to the long distance carrier chosen by the customer. [Back to Diagram]