VoIP Telephony Glossary

Below, you can find a collection and explanation of the most common terms related to Voice over IP.

A like ATA Analog Telephone Adapter

Agent: Staff member that is employed within the telephone support service of a company.
Alcatel: French company that, among other products, manufactures VoIP telephones.
Analog: Commonly used term for analog signal transmission. Analog telephony was largely replaced in Germany in the mid-1990s by digital ISDN. However, in many countries, analog telephone lines are still in use.
Analog Telephone Adapter (ATA): A device that is used to incorporate analog devices into a VoIP environment by converting analog signals into IP packets.
Appliance: Common term for the hardware that is hosting the telephony software and in combination provides a telephony server. Former term for the AskoziaPBX hardware systems that are now called telephony servers.
Applications: Asterisk applications provide the possibility to place certain program sequences for certain scenarios on specific internal or external phone numbers. An application is started by calling its respective number.
Area Code: Numeric string that defines a specific region or country as part of a telephone number. Area codes include country codes, cities or even municipalities.
AskoziaPBX: The most intuitive software PBX in the world.
Asterisk: A free computer software that offers a wide range of functions of telephone systems.
Automatic Call Distribution (ACD): In order to assure the best possible handling of incoming calls, an ACD system automatically takes and distributes calls to certain employees within a company. Particularly, call groups can be specified and assigned to the digits of the telephone keypad. An incoming call then automatically gets routed with respect to the digit pressed by the caller.

B like BLF Busy Lamp Field

Bandwidth: A defined signal processing measure that is used to describe transmission power. For IP telephony, approximately 100 Kbits per second are required respectively for upload and download for each established conversation.
Basic Rate Interface (BRI): A Base Terminal of the ISDN Technology.
Busy: SIP status that can be output when a telephone is called that is already involved in another conversation.
Busy Lamp Fields (BLF): Show the status (busy, ringing, available) of phones of other users that are connected to your phone system. Often exist in combination with speed dial keys.
Beronet: Manufacturer of telephony hardware from Berlin, Germany.

C like Conference Call

Call: Attempt to establish a telephone conversation.
Call Center: Company or department being responsible for handling incoming calls. Usually found in departments with high call volume. Outbound Call Centers perform calls to the outside world, usually calling clients and potential clients.
Call Detail Records: List of calls that have been conducted through a telephone or a PBX.
Call Flow: Graphical call schedule that allows to automatically process incoming calls. Call Flows allow easy implementation of complex telephony scenarios.
Call Flow Editor: Graphical editor that allows to implement complex call flows as diagrams easily by drag and drop.
Call Group: Logical linking of several telephony devices into groups, allowing phones within the same call group to be reached through the same phone number and ring simultaneously.
Callee: Receiver of a phone call.
Caller: Person that initiates a phone call.
Caller ID: Used to identify phones. Usually sent as a combination of name and number of the caller, it is shown on the display of the callee’s phone.
Computer Telephony Integration (CTI): Software that enables connection of VoIP phones and computers, allowing to control the functions of a telephone from a computer.
Conference Call: Merges several communication channels to allow multiple participants to join a meeting and communicate with each other at the same time.
Connection: In terms of telephony, connection usually refers to an established conversation channel for sending audio and video signals.

D like DECT Digital Enhanced Cordless Telecommunications

Dial Pattern: Combination of digits assigned to a specific decision, such as which provider to choose or whether a call is addressed internally or externally.
Dial Plan: Specifies how to interpret dialled numbers, for example as internal extensions, local numbers, long distance or International numbers.
Digital Enhanced Cordless Telecommunications (DECT): An international standard for wireless telecommunication, especially for cordless phones.
Do Not Disturb (DND): Telephone function that has all incoming calls rejected and not signalled on the device.
Dual Tone Multi Frequency (DTMF): Transmission method for telephone numbers that is used to transmit numbers through the telephone keypad. For IP telephony, SIP message are sent instead of tones.

E like Echo Cancellation

Echo Cancellation: An algorithm that can be implemented both in hardware or software and which ensures that echoes are suppressed during audio transmission through a telephone line.
External Call: General term for both incoming and outgoing calls with dialogue partners from outside of the own network.

F like Fax

Facsimile (FAX): Analog transmission of documents as images through the telephone networks.
Foreign Exchange Office (FXO): An analog interface to connect with telephone systems or providers.
Foreign Exchange Station (FXS): An analog interface to connect with devices such as telephones or fax.
Forwarding: Allows to redirect calls from one phone to another one, without the need to answer the call first.

G like Gateway

Gateway: An electronic device that can connect different network technologies with each other.
Gigaset: Manufacturer of DECT and VoIP phones from Düsseldorf, Germany

H like Headset

Handset: Part of a telephone that contains both microphone and earphone.
Headset: A combination of headphones and microphone, can be connected to a phone or to a computer to communicate through a soft phone.
Hold: If a dialogue partner is set on hold, the audio connection gets interrupted. The waiting dialogue partner can listen to hold music until being transferred or retrieved back into the conversation.
Hunt Group: Logical linking of several telephony devices. If a hunt group is called, all telephones belonging to that group ring one after the other in a pre-defined order until the call is answered or the caller hangs up.

I like IVR Interactive Voice Response

Incoming Call: External call received from the outside world on a PBX or telephone.
Integrated Services for Digital Network (ISDN): Telecommunication standard established for replacing the analog telephone network in the mid 90s, integrating both speech and data on the same communication lines.
Inter-Asterisk-Exchange (IAX): A protocol used by Asterisk telephone systems to connect between multiple Asterisk servers or between an Asterisk server and a device.
Interactive Voice Response (IVR): Enables a computer to interact with humans by using voice recognition and DTMF tones input via a phone keypad, enabling automated interaction e.g. between customers and a company’s telephone system and thus simplifying call management and forwarding.
Internal Call: A call between two users which are logged on to the same phone system, and thus does not require to build up an external connection.
Internet Protocol (IP): The principal communication protocol for delivering data packages through the internet from the source to the destination based on IP addresses.
IP Address: A numerical label assigned to each device connected to a network that uses the Internet Protocol for communication. Allows to identify and locate devices within a telecommunications network to enable data transfer.

J like Jitter

Jitter: A variation in the transmission of digital signals.

L like LDAP Lightweight Directory Access Protocol

Lightweight Directory Access Protocol (LDAP): An LDAP server typically provides a central address or phone book to the network that can be accessed by clients such as IP telephones at the same time.
Line: The term telephone line remains from the past, where a two-wire cable was required for each phone conversation.
Log: Collects system messages that provide information to the user on certain events or errors in the telephone system.

M like Music-on-Hold

MAC address: Hardware address for network-enabled devices that is set by the manufacturer of the device and can not be changed. Thus, enables a globally distinct identification of the device.
Mailbox: Also Voice Mailbox or Inbox. A Software that automatically takes calls and provides the opportunity to the caller to leave a voicemail for the callee.
Music-on-Hold: An audio file is played to callers if they have to wait in a call queue or are set on hold.

N like Night Switch

Night Switch: A function that allows to automatically activate absent message such as outside office hours or on weekends and holidays.
Network: Integration of multiple computers or other IP devices that share common services and resources and thus can communicate with each other.
Notifications: Often used as a general term for different types of system messages such as for missed calls or incoming voicemails.

O like Online/Offline

Offline: Frequent synonym for being disconnected and consequently unreachable
Online: Frequent synonym for being connected and consequently reachable
Outgoing Call: Call that leaves the internal network and lead to the outside world, becoming an external call.

P like PBX Private Branch Exchange

Private Branch Exchange (PBX): Private telephony system typically for businesses, connecting internal phones with each other as well as enabling external connections through VoIP, ISDN or analog providers.
Pickup Group: Logical linking of several telephony devices into a pickup group allows to pickup calls from other phones of this group.
Polycom: US American manufacturer of VoIP phones and other devices.
Port: The Hardware connection of a device.
Power over Ethernet (PoE): Indicates devices that are powered through the network cable or can supply other devices themselves.
Primary Rate Interface (PRI): ISDN connection type that allows up to 30 telephone channels.
Protocol: A protocol or data protocol regulates the time scheduling of data transfer as well as the conditions to be met by users to communicate through the respective protocol.
Provider: Businesses that offer services allowing among others phone calls or internet connections.
Provisioning: Configuration of an IP phone through the IP telephony server, or PBX. An automated provisioning does not require manual configurations on the phone.
Public Switched Telephony Network (PSTN): Usually refers to analog and ISDN transmissions.

Q like Call Queue

Quality of Service (QoS): Measure to ensure the quality of internet service providers by comparing the user requirements and the potential capacity of the service provider.
Queue: A call queue puts incoming calls in line until calls are available, and is typically playing on-hold music to the callers in the meantime. Several agents can be assigned and logged into a queue in order to jointly answer the calls.

R like RTP Real-Time Transport Protocol

Real-Time Transport Protocol (RTP): Data protocol for transmission of audio and video data in IP-based networks.
Request for Command (RFC): RFC documents are official documents of internet specifications, communications protocols, procedures, and events, published by the Internet Engineering Task Force (IETF) and the Internet Society. As an example, the SIP 2.0 standard was introduced in 2014 as RFC 3261.

S like SIP Session Initiation Protocol

Secure Shell (SSH): Network protocol to enable encrypted and secure connections to a remote network device and this way, for example, to access the console of the device.
Session Initiation Protocol (SIP): A network protocol for establishing and controlling connections within an IP network. SIP allows to establish telephony channels that can be used for transmitting instant messages, audio and video data using RTP.
Snom: Manufacturer of VoIP phones and other devices, located in Berlin, Germany
Softphone: Software that provides telephony functions on a PC as an alternative to SIP-based desk phones.
Speed Dial: Phone numbers or commands can be placed on speed dial keys of the telephone, allowing to call them by pressing a single key.

T like Call Transfer

Telephone: Communication device, transmitting sounds, languages and video. Available for different transmission techniques such as SIP, ISDN and analog.
Telephone Connection: The technical infrastructure provided by a network operator to connect to the public switched telephone network (PSTN) and establish phone calls.
Telephony Server: Alternative term for PBX, and furthermore referring to the AskoziaPBX hardware systems (formerly also called appliances).
Text-to-Speech (TTS): Texts are transformed into computer generated synthesised speech, for example as part of an IVR system.
Tiptel: Manufacturer of VoIP phones and other devices, located in Ratingen, Germany
Transfer: PBX function that allows to forward active calls to another callee. There are two types of transfers, blind (without notice) and attended (with notice). For blind transfers, the call is passed to the new callee without preliminary notification. Contrary, for attended transfer, the transferring party and the new callee first have a brief consultation whereas the caller is put on hold and hears music.

V like Voicemail

Videophone: A telephone with a video display that allows simultaneous video and audio transmission in real-time.
Video Codecs: Algorithms that compress and encode, or decompress and decode digital video. Once a video gets compressed to reduce its size and increase data transfer speed, it permanently loses some of it’s information, that is to say quality, dependent on the chosen video codec.
Video Telephony: The transmission of video data in parallel to speech during a telephone conversation by means of videophones.
Voicemail: Voice message by a caller that is recorded by the mailbox and can be listened to later by the callee.
Virtual Private Network (VPN): Connection between two network devices, that is secured through certification. Data transfer is encrypted in order to protect the transmitted data.

Y like Yealink

Yealink: Chinese manufacturer of VoIP telephones and other devices.

Z like Zoiper

Zoiper: Softphone supporting SIP and IAX.


Common questions about IP Phone Systems, PBX and VoIP