ADSL Asymmetric Digital
Subscriber Line: Modems attached to twisted pair copper wiring
that transmit from 1.5 Mbps to 9 Mbps downstream (to the
subscriber) and from 16 kbps to 800 kbps upstream, depending on
AGC Automatic Gain
Control is an electronic system found in many types of devices.
Its purpose is to control the gain of a system in order to
maintain some measure of performance over a changing range of
real world conditions.
ARP Address Resolution
Protocol is a protocol used by the Internet Protocol (IP)
[RFC826], specifically IPv4, to map IP network addresses to the
hardware addresses used by a data link protocol. The protocol
operates below the network layer as a part of the interface
between the OSI network and OSI link layer. It is used when IPv4
is used over Ethernet.
ATA Analog Telephone
Adapter. Used to convert analog telephone signal in order to use
a VoIP data network.
CODEC Abbreviation for
Coder-Decoder. It's an analog-to-digital (A/D) and
digital-to-analog (D/A) converter for translating the signals
from the outside world to digital, and back again.
CNG Comfort Noise
Generator, generate artificial background noise used in radio
and wireless communications to fill the silent time in a
transmission resulting from voice activity detection.
DATAGRAM A data packet
carrying its own address information so it can be independently
routed from its source to the destination computer.
DECIMATE To discard portions of a signal in order to
reduce the amount of information to be encoded or compressed.
Lossy compression algorithms ordinarily decimate while
DECT Digital Enhanced Cordless Telecommunications: A
standard developed by the European Telecommunication Standard
Institute from 1988, governing pan-European digital mobile
telephony. DECT covers wireless PBXs, telepoint, residential
cordless telephones, wireless access to the public switched
telephone network, Closed User Groups (CUGs), Local Area
Networks, and wireless local loop. The DECT Common Interface
radio standard is a multi-carrier time division multiple access,
time division duplex (MC-TDMA-TDD) radio transmission technique
using ten radio frequency channels from 1880 to 1930 MHz, each
divided into 24 time slots of 10ms, and twelve full-duplex
accesses per carrier, for a total of 120 possible combinations.
A DECT base station (an RFP, Radio Fixed Part) can transmit all
12 possible accesses (time slots) simultaneously by using
different frequencies or using only one frequency. All signaling
information is transmitted from the RFP within a multi-frame (16
frames). Voice signals are digitally encoded into a 32 Kbit/s
signal using Adaptive Differential Pulse Code Modulation.
DHCP The Dynamic Host
Configuration Protocol (DHCP) is an Internet protocol for
automating the configuration of computers that use TCP/IP. DHCP
can be used to automatically assign IP addresses, to deliver
TCP/IP stack configuration parameters such as the subnet mask
and default router, and to provide other configuration
information such as the addresses for printer, time and news
DID Direct Inward
Dialing. The ability for an outside caller to dial to a PBX
extension without going through an attendant or auto-attendant.
DNS Short for Domain Name System (or Service or Server),
an Internet service that translates domain names into IP
DSP Digital Signal Processor. A specialized CPU used for
digital signal processing. Grandstream products all have DSP
chips built inside.
DTMF Dual Tone Multi
Frequency. The standard tone-pairs used on telephone terminals
for dialing using in-band signaling. The standards define 16
tone-pairs (0-9, #, * and A-F) although most terminals support
only 12 of them (0-9, * and #).
ECHO CANCELLATION Echo
Cancellation is used in telephony to describe the process of
removing echo from a voice communication in order to improve
voice quality on a telephone call. In addition to improving
quality, this process improves bandwidth savings achieved
through silence suppression by preventing echo from traveling
across a network. There are two types of echo of relevance in
telephony: acoustic echo and hybrid echo. Speech compression
techniques and digital processing delay often contribute to echo
generation in telephone networks.
FQDN Fully Qualified
Domain Name. A FQDN consists of a host and domain name,
including top-level domain. For example, www.grandstream.com is
a fully qualified domain name. www is the host, Grandstream is
the second-level domain, and and.com is the top level domain.
FXO Foreign eXchange Office. An FXO device can be an
analog phone, answering machine, fax, or anything that handles a
call from the telephone company like AT&T. They should also
operate the same way when connected to an FXS interface.
FXS Foreign eXchange
Station. An FXS device has hardware to generate the ring signal
to the FXO extension (usually an analog phone).
An FXS device will allow
any FXO device to operate as if it were connected to the
phone company. This makes your PBX the POTS+PSTN for the
The FXS Interface connects
to FXO devices (by an FXO interface, of course).
H.323 A suite of
standards for multimedia conferences on traditional
HTTP Hyper Text
Transfer Protocol; the World Wide Web protocol that performs the
request and retrieve functions of a server.
IP Internet Protocol. A
packet-based protocol for delivering data across networks.
IP-PBX IP-based Private
IP Telephony (Internet
Protocol telephony, also known as Voice over IP Telephony) A
general term for the technologies that use the Internet
Protocol's packet-switched connections to exchange voice, fax,
and other forms of information that have traditionally been
carried over the dedicated circuit-switched connections of the
public switched telephone network (PSTN). The basic steps
involved in originating an IP Telephony call are conversion of
the analog voice signal to digital format and
compression/translation of the signal into Internet protocol
(IP) packets for transmission over the Internet or other
packet-switched networks; the process is reversed at the
receiving end. The terms IP Telephony and Internet Telephony are
often used to mean the same; however, they are not 100 per cent
interchangeable, since Internet is only a subcase of
packet-switched networks. For users who have free or fixed-price
Internet access, IP Telephony software essentially provides free
telephone calls anywhere in the world. However, the challenge of
IP Telephony is maintaining the quality of service expected by
subscribers. Session border controllers resolve this issue by
providing quality assurance comparable to legacy telephone
IVR IVR is a software application that accepts a
combination of voice telephone input and touch-tone keypad
selection and provides appropriate responses in the form of
voice, fax, callback, e-mail and perhaps other media.
MTU A Maximum
Transmission Unit (MTU) is the largest size packet or
frame, specified in octets (eight-bit bytes), that can be sent
in a packet- or frame-based network such as the Internet. The
maximum for Ethernet is 1500 byte.
NAT Network Address
NTP Network Time
Protocol, a protocol to exchange and synchronize time over
networks The port used is UDP 123 Grandstream products using NTP
to get time from Internet.
OBP/SBC Outbound Proxy
or another name Session Border Controller. A device used in VoIP
networks. OBP/SBCs are put into the signaling and media path
between calling and called party. The OBP/SBC acts as if it was
the called VoIP phone and places a second call to the called
party. The effect of this behavior is that not only the
signaling traffic, but also the media traffic (voice, video etc)
crosses the OBP/SBC. Without an OBP/SBC, the media traffic
travels directly between the VoIP phones. Private OBP/SBCs are
used along with firewalls to enable VoIP calls to and from a
protected enterprise network. Public VoIP service providers use
OBP/SBCs to allow the use of VoIP protocols from private
networks with internet connections using NAT.
Protocol over Ethernet is a network protocol for encapsulating
PPP frames in Ethernet frames. It is used mainly with cable
modem and DSL services.
PSTN Public Switched
Telephone Network. The phone service we use for every ordinary
phone call, or called POT (Plain Old Telephone), or circuit
Transport Control Protocol, defined in RFC 3550, a sister
protocol of the Real-time Transport Protocol (RTP), It partners
RTP in the delivery and packaging of multimedia data, but does
not transport any data itself. It is used periodically to
transmit control packets to participants in a streaming
multimedia session. The primary function of RTCP is to provide
feedback on the quality of service being provided by RTP.
RTP Real-time Transport
Protocol defines a standardized packet format for delivering
audio and video over the Internet. It was developed by the
Audio-Video Transport Working Group of the IETF and first
published in 1996 as RFC 1889.
SDP Session Description
Protocol is a format for describing streaming media
initialization parameters. It has been published by the IETF as
SIP Session Initiation Protocol, An IP telephony signaling
protocol developed by the IETF (RFC3261). SIP is a text-based
protocol suitable for integrated voice-data applications. SIP is
designed for voice transmission and uses fewer resources and is
considerably less complex than H.323. All Grandstream products
are SIP based
STUN Simple Traversal of UDP over NATs is a network
protocol allowing clients behind NAT (or multiple NATs) to find
out its public address, the type of NAT it is behind and the
internet side port associated by the NAT with a particular local
port. This information is used to set up UDP communication
between two hosts that are both behind NAT routers. The protocol
is defined in RFC 3489. STUN will usually work well with
non-symmetric NAT routers.
TCP Transmission Control Protocol is one of the core protocols
of the Internet protocol suite. Using TCP, applications on
networked hosts can create connections to one another, over
which they can exchange data or packets. The protocol guarantees
reliable and in-order delivery of sender to receiver data.
TFTP Trivial File
Transfer Protocol, is a very simple file transfer protocol, with
the functionality of a very basic form of FTP; It uses UDP (port
69) as its transport protocol.
UDP User Datagram
Protocol (UDP) is one of the core protocols of the Internet
protocol suite. Using UDP, programs on networked computers can
send short messages known as datagrams to one another. UDP does
not provide the reliability and ordering guarantees that TCP
does; datagrams may arrive out of order or go missing without
notice. However, as a result, UDP is faster and more efficient
for many lightweight or time-sensitive purposes.
VAD Voice Activity
Detection or Voice Activity Detector is an algorithm used in
speech processing wherein, the presence or absence of human
speech is detected from the audio samples.
VLAN A virtual LAN,
known as a VLAN, is a logically-independent network. Several
VLANs can co-exist on a single physical switch. It is usually
refer to the IEEE 802.1Q tagging protocol.
VoIP Voice over the
Internet. VoIP encompasses many protocols. All the protocols do
some form of signaling of call capabilities and transport of
voice data from one point to another. e.g.: SIP, H.323, etc.