B

Basic Rate Interface - a telephony interface standard that has two 64kb/sec data channels (called "B" channels) and one 16kb/sec control channel (called the "D" channel). This standard is commonly used for delivering ISDN digital telephony services to customer premises over a 2-wire interface.

Bayonne - an IVR and telephony server available under the Gnu Public License. See http://www.gnu.org/software/bayonne/bayonne.html

Billing - ?

BRI - acronym for Basic Rate Interface

C

Call Rating - ?

Call Supervision - ?

CDR - acronym for Call Detail Record

Channel Bank - a device that splits a Primary Rate Interface into 24 or 32 individual channels

Codec - concatenation of "coder" and "decoder". A device, or software element, that encodes or decodes a video or audio signal. See also G.711, G.722, G.723.1, G.726, G.728, G.729, H.261, H.263, H.264, iLBC, Speex, GSM 06.10

Comfort Noise - ?

CPE - acronym for Customer Premises Equipment

CPhone - an Open Source soft phone using H.323 for Unix and Windows available under the Mozilla Public License. See http://www.cphone.org

D

Dialtone generation - 

DTMF - acronym for Dual Tone Multi-Frequency

Dual Tone Multi-Frequency - 

E

E1 - A Primary Rate Interface telephony interface standard consisting of 32 voice/datachannels each of 64kb/sec, giving a total of 2048 kb/sec. This is available in Europe and Australia, as opposed to a T1 used in North America. See also J1, channel bank

Echo Cancellation -

Endpoint - 

F

Frame - ?

Frame Erasure - ?

Free World Dialup - an addressing and routing network operated by Jeff Pulver. It uses the SIP protocol, and there is no charge to signup. It provides limited interoperation with other SIP networks and some toll-free PSTN numbers. See http://www.fwd.pulver.com/

Free Software Foundation - Organisation behind the Gnu Public License. See http://www.gnu.org

FSF - acronym for Free Software Foundation. 

FWD - acronym for Free World Dialup

G

G.711 - an ITU standard for a narrow-band audio codec that encodes speech into a stream of 8 bit samples (or less frequently 7 bit samples) at 8khz. This creates a data stream at either 64kb/sec or 56kb/sec. G.711 uses a logarithmic mapping that emphasises the parts of the signal that the human ear is most sensitive to. There are two variants with different mapping functions: ALaw which is used with E1 connections (Europe and Australia), and µlaw which is used with T1 and J1 connections. See also mulaw, ulaw

G.722 - an ITU standard for a wideband audio codec that encodes speech into a 64kb/sec, 48kb/sec or 32kb/sec data stream at 16khz. 

G.723.1 - an ITU standard for a narrow-band audio codec that encodes speech into a stream of data frames that each represents 30ms (240 samples) of speech data. Each frame can be either 24 or 20 bytes long, which makes the data stream either 6.4kb/sec or 5.3kb/sec. This codec algorithm is covered by a variety of patents, means that a license free must be paid before it can be used commercially.

G.726 - an ITU standard for a narrow-band audio codec that encodes speech into a stream of 2, 3, 4, or 5 bit samples, giving a data stream of at 16kb/sec, 24kb/sec, 32kb/sec, or 40kb/sec. 

G.728 - an ITU standard for a narrow-band audio codec that encodes speech into a stream of 10 bit frames that each represent 5 samples, giving a data stream of 16kb/sec. This codec algorithm is covered by a variety of patents, which means that a license free must be paid before it can be used commercially.

G.729 - an ITU standard for a narrow-band audio codec that encodes speech into a stream of data frames that each represent 10ms (80 samples) of speech data. Each frame is 10 bytes, giving a data stream of 8kb/sec. This codec algorithm is covered by a variety of patents, means that a license free must be paid before it can be used commercially. 

Gatekeeper - a H.323 network element that provides routing and authentication services to endpoints within a network zone. 

Gateway - a generic term for a network element to provides an interface between two networks that use different protocols. Examples include a H.323 to PSTN gateway, or a SIP to H.323 gateway 

GnomeMeeting - an Open Source softphone client for Linux that supports audio and video. See http://www.gnomemeeting.org 

Gnu Public License - One of the most popular Open Source licenses, created by the Free Software Foundation and the only one with a full-time evangelist in the person of Richard Stallman. See FSF, http://www.gnu.org, GPL

GPL - acronym for Gnu Public License. 

GSM - acronym for Global System for Mobile communication. 1) Refers to the GSM 06.10 audio codec; 2) refers to the GSM digital cellphone standard

GSM 06.10 - a narrow-band audio codec that encodes speech into a stream of data frames that each represent 20ms (160 samples) of speech data. Each frame is 264 bits, giving a data stream of 13.2kb/sec. This codec algorithm is claimed to be patented by Philips, but is used by several companies. An Open Source implementation is available from http://kbs.cs.tu-berlin.de/~jutta/toast.html

H

H.261 - an ITU standard for video encoding that corresponds roughly to the MPEG-1 video standard 

H.263 - an ITU standard for video encoding that corresponds roughly to the MPEG-2 video standard

H.264 - an ITU standard for video encoding that corresponds roughly to the MPEG-4 video standard

H.323 - an ITU standard for establishing and controlling multi-media sessions over packet-switched networks. H.323 was one of the original VoIP protocols, and is seen by proponents of SIP as the "old guard" that must be replaced. The OpenH323 and OPAL projects offer excellent Open Source implementations of this protocol.

I

IAX - acronym for Inter-Asterisk-eXchange protocol

iLBC

International Telecommunications Union - an internation standards body based in Geneva, Switerland that publishes and coordinates many of the standards used for VoIP, including the H.x series of protocols and the G.x series of audio codec algorithms. See http://www.itu.int

IP-Phone

ISDN

ITU - acronym for International Telecommunications Union

ITSP

IVR

J

J1 - A Primary Rate Interface standard peculiar to Japan. This is a variant of the E1 telephony interface standard providing 24 voice/data channels over 2048 kb/sec

Jitter

Jitter Buffer

K

KPhone

L

Latency

LCR

Linphone

M

Media Channel

MGCP

Mozilla Public License - an Open Source license created as part of the Mozilla web browser project. This is the license used by the OpenH323 and OPAL projects

MPL - acronym for Mozilla Public License

mulaw - alternate spelling of µlaw, which is one of the two variants of G.711 speech encoding algorithm. Also known as uLaw

Narrowband

N

Narrow-band audio codec

NAT Traversal

NT

O

ohphone

OPAL

OpenH323

oSIP

P

PABX - Acronym for Private Automatic Branch Exchange. A PBX that uses automatic switching, as opposed to one that uses manual switching (see picture below)

See also PBX

PBX - Acronym for Private Branch Exchange. A telephony switching device located on the customer's premises, as opposed to being located in the carriers exchange building.

Packet Loss

PCM

PDD - acronym for Post Dial Delay

PDU

POTS - acronym for Plain Old Telephone System

PRI - acronym for Primary Rate Interface

Primary Rate Interface - an E1, T1 or J1 voice/data connection

Protocol

Proxy

PSTN - acronym for Public Switched Telephone Network

Q

R

Registrar

RFC2833

RTP

S

SCCP

Signalling Channel

Silence Detection

Silence Removal

SIP

Sipura

Skype

Soft phone

Speex

STUN

Switch

T

T1 - A Primary Rate Interface telephony interface standard consisting of 24 voice/data channels each of 64kb/sec, giving a total of 1536 kb/sec. This is available mainly in the US, as opposed to an E1 that used in Europe and Australia. See also J1, channel bank

TDM

TE

Terminal

U

ulaw - alternate spelling of µlaw, which is one of the two variants of the G.711 speech encoding algorithm. Also known as muLaw

V

VLEC

VoFR

VoIP

Vonage

W

Wideband audio codec

X

Y

YATE

Z

Other

µlaw -one of two different variants of the G.711 codec. Used primarily on on T1 connections. See also Alaw