IVR Glossary




A&B Bits

These are the signaling bites used in a telephony environment to signal information.

A&B Signaling

Used in a T1 call to carry dialing and control information.

ACD (automatic call distributor)

This is another name for private branch exchange (PBX). The ACD: answers calls, looks in a database for instructions, will send the call based on instructions to a recording, “Hello, thank you for calling…” or send the call to a hunt group or operator.

ANI (automatic number identification)

The number of the person calling. This is what is displayed on your phone before you answer the call.

API (application programming interface)

A series of functions supplied by a card vendor to allow interaction with their drivers. Most vendors have a series of APIs. In VBVoice™ we use the API to talk to the card.

ASR (automated speech recognition)

It incorporates knowledge and research in the linguistics, computer science, and electrical engineering fields.


Telephone transmissions that are not digital (plain old telephone system or service [POTS]).

Analog/Digital Converter (also known as A-to-D converter)

Converts signals from analog to digital and reverse. See Multiplexer.

Asynchronous Mode

When a function call or task is simply called, like playing a waveform audio (WAV) file, and the process returns to the main thread and waits for notification that the process has completed. Term is used mainly in database lookups where the main thread is not locked while the system waits for results.

Auto Attendant

The interactive voice response (IVR) application that answers and directs all incoming calls.


B Channel

An integrated services for digital network (ISDN) channel used to convey audio or data rather than signaling. See D channel.

Baby Bell

Local phone companies in the US responsible for local calls.

Basic Rate Interface

Uses just one B channel for audio and one D channel for data (two channels or lines). Mainly used in Europe and it’s as cheap as analog.

Battery or UPS (uninterrupted power supply)

All phone systems run on DC power. They all have battery power backups and use this to smooth the AC power dips and spikes.


A tone to signal line is in use.


CAS (channel associated signaling)

A form of out-of-band signaling used in both T1 and E1. It’s a type of ISDN protocol.

CO (central office)

Be it Bell, ITT, Qwest, Sprint, etc.

CO Simulator

A test unit that acts like a mini CO. Supplies tones, disconnect signals, simulates on-hook off-hook, etc.

CSU (channel service unit)

A CSU is required in most cases when connecting directly to the public T1 network. The CSU provides functions such as loopback capabilities for running diagnostic tests to locate where problem conditions are occurring on the T1 chain. Some CSU’s have dialing capability for performing remote diagnostics. The CSU is the last point where the signal is regenerated as it leaves the network.

It also provides line equalization and voltage protection for telephone company and customer premise equipment, monitors the T1 line for violations and can generate "keep alive" signals and error condition messages Keep alive,also known as a persistent connection, allows files to be transferred from a web server to a web browser without interruption.

CTI (computer telephony integration)

General term for personal computers and phone board configurations used to create IVRs.


In voice processing cadence is the pattern of sound and silence generated in an audio signal. Examples are busy and ring tones. One second of tone followed by three seconds of silence to signify a ring.

Call Center

A business where calls are answered or made. Can be as small as one person or as big as hundreds o agents.

Call Completion

In telephony this is when two parties are connected. A complete circuit has been made.

Call Progress Analysis or Supervision

This is the technology that listens for tones being returned by the network to indicate what is happening during a call. For example, using call progress analysis is what is used to determine the results of an outbound call.

Call Progress Monitoring

Analogous to call progress analysis, but call progress monitoring may need to be active during the entire call. Reasons may be that the network isn’t returning a disconnect signal that the board is expecting and it may have to listen for a dial tone to recognize a disconnect.

Call Progress Tone

Busy tone, dial tone, ring tone, etc.

Called ID


Caller ID

See ANI.


A line, a single path of communication. Not to be confused with ports.

Channel Bank

Also called a T1 Multiplexer (MUX). A device at a telephone company CO that converts analog signals from home and business users into digital signals to be carried over higher speed lines between the CO and other exchanges.


A term used in ASR when some consonants are omitted during normal conversation. For example, seven nine and test tube. They’re pronounced seven-ine and test-ube. Hard for discrete recognizers.


A function for converting and compressing audio signals.


The changing of information to use less space (fewer bits) to transmit data. Part of different codecs (e.g., G723, G729, etc).


Where three or more talkers can speak or hear each other.

Continuous Speech

A term used to describe speech that comes in a relatively short period of time. Can include coarticulation.

Custom Control

A special interface element, like a button or scroll bar made by a third party. VBVoice is an example of a series of custom controls.


D Channel

Data channel on an ISDN line. Used to transmit calling information like dialed digits. This form of out-of-band processing allows for faster responses.

DNIS (dialed number information service)

This is the called number. Used to route calls if a business has more than one posted number.

DSP (digital signal processor)

Specialized chip to do realtime processing of audio or video. DSPs are found on most phone cards.

DTMF (dual tone multifrequency)

Term for the tones generated by pushing buttons.

DTMF Cut-through

Ability to respond immediately to a received DTMF tone even when playing a prompt.

Dial String

The string of characters used to represent a dialing process. They will either be numbers for DTMF transmission or URL address for VoIP transmission.

Dial Tone

The sound you hear when you pick up the phone. Provided by either the CO or your PBX.

Digital Trunk

Generic name for the T1/E1 line. Transmission is digital, not analog.


The signal to indicate that one party has hung up.



European digital lines.


Something that happens during a call flow. Events are where code is placed so that it is tripped at the appropriate time during the call flow.


Fast Busy

A tone generated and is twice as fast as a busy tone.

Fax Broadcast

Where one copy of a document is sent to several phone numbers.

Fax Synthesis

Ability to create a fax document from database information only.


Used to provide hard copy of information to a caller. For example, doctor calls insurance company, patient’s policy number is entered, doctor’s fax number is entered and hard copy of coverage is faxed back to doctor.


The strand of glass wire used in optical cable.


A brief on-hook period to place a call into a hold. It’s produced by depressing the hook switch. Can be done from a card.



When you make a phone call at the same time someone is trying to call you. Before it rings you pick up the handset and somebody who was calling you is on the line saying, “Hello Hello”. This is glare.

Grunt Detection

A crude form of voice detection that responds to sound or silence. Doesn’t understand speech.



The process of a call reaching a group of lines.

Hunt Group

The way several lines are organized so that calls are routed to a free line. Groups are common in sales, tech support and most departments where several people do the same job.


ISDN (integrated services digital network)

A set of communication standards for simultaneous digital transmission of voice, video, data and other network services over the traditional circuits of the public switched telephone network.

ISP (internet service provider)

The portal to internet access. Needs to supply features for VoIP transport.

IVR (interactive voice response)

This is what answers the phone in an automated system.

In-band Signaling

Signaling that doesn’t need a second channel. Examples are touch tone digits, which are on the same channel. T1 Robbed bit is also in-band.


Loop Current

Current that flows when there is a live connection through an analog phone line.


MRCP (media resource control protocol)

A standardized communication protocol used by speech servers to provide TTS and ASR services to their clients.

MUX (multiplexer)

A device that selects one of several analog or digital input signals and forwards the selected input into a single line.

MVIP (multi vendor integration protocol)

Usually refers to Mitel’s voice bus; has been adopted by other non-Dialogic vendors. Term is used in VBVoice to force MVIP for conferencing (MVIPBridging = yes or no).


A folder or file where messages are stored for a single owner.


A list or selection choice. Used to refer to choices given in an IVR. For example Press 1 for … Press 2 for…

Mezzanine Bus

Used to transmit information between multiple cards in the same machine (e.g., SC Bus, H100 Bus).

Mu-Law Encoding (also called U-Law)

The encoding used for wav files used by North American phone system phrases.


OCX (object linking and embedding control extension)

The file extension of an Active X control. VBVoice uses OCX files for most of its controls.

OLE (object linking and embedding) Control

Custom controls use OLE interfaces to talk to Active X or OCX code.


When you lift the receiver the line has gone OffHook. Alerts the PBX or CO that the user will want to do something.


Phone is on its cradle. Line is not active.

OnHook Dialing

Allows a caller to dial without going off-hook. Not very common.

Operator Intercept

When invalid numbers are dialed or an error condition occurs an operator intercept may occur. A SIT is played followed by the message explaining the problem.

Out-of-band Signaling

The signaling is on a separate channel from the one carrying voice or data.


PABX or PBX (private [automatic] branch exchange)

Often referred to as a switch. Does phone switching for a business.

PAMD or PVD (positive [answering] machine detection)

Algorithm used to detect whether a person answered a phone or not.

POTS (plain old telephone system or service)

An analog telephone service implemented over copper twisted pair wires and based on the Bell system.

PRI (primary rate interface)

Is the ISDN equivalent of a T1 circuit. All ISDN lines are PRI.

PSTN (public switched telephone network)

Worldwide telephone network run by private companies (e.g., Bell, AT&T, Qwest, Sprint, etc).


Service where a caller is charged for the service provided/information (e.g., weather, stock prices, sports scores, etc).

Power or Predictive Dialer

Automated system that makes outbound calls. When the call is answered it transfers the call to an agent.

Pulse Dialing

Old rotary dialing system.

Pulse-to-tone Converter

A device that recognizes the clicks of a rotary dial and translates it to tone. Used to be present on older boards.



The four-wire connector used on most phones.


The network connector used to connect T1 lines. Also network cables.


The event that triggers a phone call. A device receives a voltage charge in analog or a bit switch in T1 and it has been programmed to understand that this is an incoming call.


SDK (software development kit)

A set of libraries and documentation needed to create applications using an operating system.

SIT (special information tone)

In telephony, a SIT is an inband international standard signal consisting of three rising tones indicating a call has failed. It usually precedes a recorded announcement describing the problem.


The process of grabbing a line prior to making a call.

Span Line

A T1 line.


Another term for automated speech recognition.

Station Card

A specialized card that can send a voltage to a handset to cause it to ring. It is used in call centers.

Supervised Transfers

A call transfer made by an automated device that attempts to determine the results (i.e., answer, busy, etc).



Digital transmission line.

TAPI (telephone application programming language)

Microsoft’s API for telephone. Mainly used by Mitel to connect IVR to their switch.

TDM (time division multiplexing)

A method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern. It is used when the data rate of the transmission medium exceeds that of signal to be transmitted.

TTS (Text-to-speech)

Process of converting text to audio.


URL (uniform resource locator)

Known as a web address; a web resource that specifies its location on a computer network and a mechanism for retrieving it.



A system that records messages and stores them for later retrieval.

Voice Recognition

Ability of a machine to understand human speech (known as ASR). Nuance and LumenVox are examples.

Voice Board

Another name for phone board. A add in board to allow telephone processing in a PC.

VM (virtual machine)

A software implementation of a machine (i.e., a computer) that executes programs like a physical machine.


A tool embedded in VBVoice that enables all VBVoice controls to develop a call flow that can process both voice calls and data sessions from a browser supporting HTML 5.

Visual IVR

A visual representation of an IVR call menu on a customer's smartphone or computer screen.



A signal that is sent in a T1 transmission to signal a call is coming.


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