G
LOSSARY OF
V
O
IP
T
ERMS
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 line distance.
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
Analogue Telephone Adapter. Covert analogue telephone to be used in data network for VoIP, like
Grandstream HT series products.
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 sub-sampling.
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.
DNS
Short for
Domain Name System
(or
Service
or
Server
), an
Internet
service that translates
domain
names
into IP addresses
DID
Direct Inward Dialing. The ability for an outside caller to dial to a PBX extension without going
through an attendant or auto-attendant.
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 #).
Grandstream Networks, Inc.
HT488 User Manual
Page
30 of 33
Firmware 1.0.3.64
Last Updated: 4/2007
