VoIP Glossary for Decision Makers

Attendant (Auto Attendant)

An automatic response system that handles incoming calls and sends them to the appropriate phone or message: “…press 2 for sales, 5 for the Operator…”

BYOD (Bring Your Own Device)

Some VoIP providers allow a person to supply their own equipment.

Cloud Communications

Cloud refers to the Internet. Cloud Communications uses the Internet as a means of communication. Also known as, hosted VoIP or Internet Phone Service.

DID (Direct Inward Dialing)

A service that allows an enterprise to allocate individual phone numbers to each person within its PBX system.

IVR (Interactive Voice Response)

An integrated software information system that speaks to callers and uses menus and voice responses. By using touch-tone keypad entries to interact with the software, you can integrate voice responses with real time data.

LERG (Local Exchange Routing Guide)

A database of the first 6 digits of a telephone number, updated on a regular basis, that provides information for routing telephone calls over the Public Switching Telephone Network, as well as, enables identification of what local company owns the number.

LNP (Local Number Portability)

The ability of a US telephone customer to retain their phone number if they switch to another local telephone provider.

PBX (Public Branch Exchange)

A private telephone switching system that allows outside phone lines from a telecommunications provider to connect to extensions within the office or building. They usually have multiple features including call forwarding, rollover, paging and voice mail.

POTS (Plain Old Telephone System)

The familiar single phone line, single phone number system.

PSTN (Public Switched Telephone Service)

The combination of local, long-distance and international carriers that make up the worldwide telephone network.

Rate Center

The geographic area used by local exchange carriers to set rate boundaries for issuing phone numbers and for billing. Rate centers are important when considering porting of numbers through LNP to and from VoIP service providers.

SIP (Session Initiation Protocol)

A signaling protocol for Internet conferencing, telephony, and instant messaging that merges voice with other data.

SIP Trunking

The use of VoIP to facilitate the connection of typically a PBX to the Internet, where the Internet replaces the conventional telephone trunk, allowing a business to communicate with traditional PSTN telephone subscribers worldwide by connecting to an ITSP (Internet Telephony Service Provider).

Soft Phone

IP telephony software that allows end users to send and receive calls over the computer or handheld PC device (PDA) over the Internet. Typically used with a headset and microphone. Hard IP phones refer to desk phones that are equipped for VoIP.

VoIP (Voice over Internet Protocol)

The transmission of voice over the Internet as digital packets rather than the traditional circuit-committed protocols of the PSTN. VoIP uses real-time protocol (RTP) to help ensure that the packets get delivered in a timely way.

VoIP Equipment and Technical Glossary

ATA (Analog Telephone adapter)

A device that converts analog voice signals to digital signals which can then be transmitted over the Internet.


Usually measured in 1000 bits per second (kbps), it is the amount of data that can be carried from one point to another in a given time period.


One signaling element per second, not to be confused with bits per second.

CDR (Call Detail Record)

Details about a specific call that includes duration, origination, destination, and billable information, and more.

CPE (Customer Premises Equipment)

Equipment at the customer’s location that converts the digital signal back to voice.

CSR (Customer Service Record)

A document required for all phone numbers, the CSR shows information that is tied to that number including services, billing activity, associated address and service orders.

DTMF (Dual Tone Multi-frequency)

Also known as Touchtone, DTMF is the signal generated when you press a telephone’s touch keys. These signals are actually two tones of a specific frequency designed so that a voice cannot duplicate them. The ability for interactive telephone menus to work correctly across different networks and phone systems is due to the fact that DTMF tones are standardized and are uniquely linked to a number, “#” or “*” on the telephone keypad.

MTA (Multimedia Terminal Adapter)

A device that connects a traditional telephone to a cable line, converting analog voice to digital signals.

PRI (Primary Rate Interface)

Typically a dynamic circuit that delivers both voice and data, giving preference for voice. When a channel is not carrying voice it is automatically allocated for data.

RTP (Real Time Transport Protocol)

An Internet protocol that functions for end-to-end network connections for applications that use audio or video.

Soft Phone

IP telephony software that allows end users to send and receive calls over the computer or handheld PC device (PDA) over the Internet. Typically used with a headset and microphone. Hard IP phones refer to desk phones that are equipped for VoIP.