.JPG
: JPEG (usually pronounced JAY-pehg) is a term
for any graphic image file produced by using a JPEG
standard. |
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1G
: Also known as: First Generation 1G (First
Generation) is the name given to the first generation of mobile
telephone networks. These systems used analogue circuit-switched
technology, with FDMA (Frequency Division Multiple Access), and
worked mainly in the 800-900 MHz frequency bands. The networks had
a low traffic capacity, unreliable handover, poor voice quality,
and poor security. As the 1G networks became obsolete, their
frequencies were auctioned off for use in 2G and 3G networks.
Examples of these first generation mobile phone networks are AMPS
(Advanced Mobile Phone Service), TACS/ETACS (Total Access
Communications System / Extended Total Access Communications
System), NMT 450 (Nordic Mobile Telephone System) and NTT (Nippon
Telegraph and Telephone System). |
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2.5G
: Also known as: Second Generation 2G (Second
Generation) is the generic term used to refer to the second
generation of wireless mobile telephone networks, which were the
first to feature purely digital technology. As demands for the
quality and quantity of mobile communication services increased, 2G
systems were the logical next stage in the evolution from the 1G
(first generation) analogue systems. Typical characteristics of 2G
include roaming, better high-bit-rate voice quality, improved
security with different levels of encryption, the ability to convey
some data (e.g. SMS) as well as speech, and a wider selection of
subscriber services. Examples of the major second generation
digital mobile telephony systems are: GSM (Global System for Mobile
Communications) in Europe, IS-95 (CDMAone) and IS-136 (D-AMPS /
TDMA) in the USA, and PDC (Personal Digital Cellular) in
Japan |
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2G
: Also known as: Second Generation 2G (Second
Generation) is the generic term used to refer to the second
generation of wireless mobile telephone networks, which were the
first to feature purely digital technology. As demands for the
quality and quantity of mobile communication services increased, 2G
systems were the logical next stage in the evolution from the 1G
(first generation) analogue systems. Typical characteristics of 2G
include roaming, better high-bit-rate voice quality, improved
security with different levels of encryption, the ability to convey
some data (e.g. SMS) as well as speech, and a wider selection of
subscriber services. Examples of the major second generation
digital mobile telephony systems are: GSM (Global System for Mobile
Communications) in Europe, IS-95 (CDMAone) and IS-136 (D-AMPS /
TDMA) in the USA, and PDC (Personal Digital Cellular) in
Japan |
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3-Way Calling
: Also known as: Conference Call 3-Way Calling
(Conference Call) is a network facility that enables three or more
parties to be connected together in a conference call, so that they
may all speak and listen simultaneously. This is often used as a
convenient substitute for a physical meeting, as the participants
can be located in different towns, or even in different countries.
This feature is very useful when two friends are having a
conversation and they need to ask questions of a third person
instead of hanging up and calling back, the third party can be
dialled during the course of the conversation to set up a
conference call |
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3G
: Also known as: Third Generation 3G (Third
Generation) is a generic term used to refer to the latest standard
of wireless mobile telephone networks. Third Generation phones are
capable of the high data rates, wide bandwidth and increased
capacity needed to support the new range of digital services
available for mobile devices, such as Internet access, multimedia
applications, and support for global roaming. The major multiple
access transmission technique used in 3G is CDMA, a
packet-switching technology, which provides a more efficient use of
the available spectrum than did the earlier methods of FDMA and
TDMA. The two main 3G technologies used are UMTS with wideband CDMA
(W-CDMA) in Europe, and cdma2000™ with multi-carrier CDMA (MC-CDMA)
in the USA. Many 3G systems will operate in the 2 GHz frequency
band, and are designed to provide a range of data rates from 144
kbps to 2 Mbps, depending on the user's location and circumstances.
The 3G mobile communications standard was a programme led
originally by the ITU under the IMT-2000 project, and handsets and
networks are now generally defined as UMTS (Universal Mobile
Telecommunication Service). However, despite the intention that the
IMT-2000 specification would result in a single, unified 3G system,
several different versions of 3G have developed due to the leading
telecommunications companies choosing to take a more evolutionary
approach to upgrading their networks |
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A5
: A5 is the encryption algorithm commonly used
by GSM networks in Europe. It has a 64-bit key, although in
practice at least ten of these bits are unused. A weaker version of
A5 called A5/2 is exported to some countries, including Australia.
It was originally a secret algorithm but was eventually leaked,
which helped the case for using the open Kasumi algorithm as a
replacement for A5. Comp128 is the more common GSM alternative to
A5 |
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AAC
: advanced analogue coding |
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Abandoned Call
: Abandoned call is one in which a connection is
made with the recipient, but the caller then decides to terminate
the call before any proper communication is established.
Organisations usually wish to keep abandoned calls to a minimum, as
they may indicate a slow response to incoming calls |
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AC Wall Charger
: AC Wall Charger is an essential accessory for
use with mobile�phones and other electronic devices. The charger
enables the mobile device to be powered, and for its battery to be
recharged, by connecting it to a mains electricity supply socket.
AC wall chargers are often the only means of recharging the
battery, and are usually supplied with a phone as they are designed
to work with a particular product or type of battery. Wall chargers
should not be interchanged without first taking advice, or
expensive damage could result. Also note that it is normal for
chargers to get warm while in use |
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Access Grant Channel
: Also known as: AGCH Access Grant Channel
(AGCH) is a downlink channel (base to mobile) used by a BS (Base
Station) to tell the MS (Mobile Station) which DCCH (Dedicated
Control Channel) to use, after the MS has previously requested
access to the network by sending a message over the RACH (Random
Access Channel). The AGCH is used to assign resources to the user
who has requested access to the network, and the BS allocates a TCH
(Traffic Channel) or SDCCH (Stand-Alone Dedicated Control Channel)
to the MS, allowing it access to the network |
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ACELP
: Also known as: Algebraic Code Excited Linear
Prediction Algebraic Code Excited Linear Prediction, or ACELP, is a
speech compression system, used to provide a good standard of
speech quality when the network is operating at low data rates
(i.e. narrow bandwidth). The analogue voice signal is converted to
a digital data signal, so that it can be compressed for
transmission over the network, and the process is then reversed at
the other end when the digital data is converted back to an
analogue voice signal. The quality of the reproduced speech will
appear to be much better at the receiving phone than would have
been the case if an ACELP system had not been used. The technology
associated with ACELP is defined by the ITU-T (International
Telecommunications Union-Telecommunication Standardization Sector)
and this has been used for a long time as a standard on the
Internet for voice applications, being integrated into software
such as Microsofts MediaPlayer?. |
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Action Script
: ActionScript is an ECMAScript-based
programming language used for scripting Adobe Flash movies and
applications. |
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ActionScript
:
an ActionScript is the the language
used in the Macromedia Flash program.
Look in the help menu in Macromedia Flash for more detailed
information.
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Active Matrix
: Also known as: Thin Film Transistor, TFT TFT
(Thin Film Transistor or Active Matrix) LCD is a mass produced
display technology that offers improved refresh rates and good
contrast over passive matrix displays. It achieves this by adding
an individual switch at every single pixel, which means that
voltage can be actively supplied to individual pixels instead of
one row and one column receiving current at a time. A thin film
transistor at each pixel allows much greater contrast and vastly
improved refresh rates compared with older displays. This makes
full motion video feasible with an active matrix. The two
disadvantages to TFT displays are that they have higher power
consumption as each individual pixel drains current, and they are
more expensive; it is not cheap to manufacture perfect large sheets
of transistors, as current processes are low-yield |
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Adaptive Differential Pulse Code
Modulation
: Also known as: ADPCM Adaptive Differential
Pulse Code Modulation (ADPCM) is a compression/decompression
technique, used for converting analogue sound or data into a string
of digital binary code. Frequent samples are taken of the analogue
signal, and the difference between the actual value of each sample
and its predicted value (derived from the previous samples) is
quantized and converted to a digital signal. This technique is
called 'adaptive', because the encoding predictions are adjusted in
accordance with the changing characteristics of the input signal,
and the coding scale is modified to accommodate any large or small
differences. The ADPCM method of encoding takes up less storage
space, and produces a lower bit rate, than standard PCM (Pulse Code
Modulation). This greater efficiency is achieved because only the
differences between samples are recorded. At the decoder the
quantized difference signal is added to the predicted signal to
produce the reconstructed speech signal. ADPCM can typically give a
compression ratio of 4:1, and one version of ADPCM is used to
encode audio and compress more data onto Sony's Mini Discs |
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ADC
: analogue to digital converter |
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ADSL
: Also known as: Asymmetric Digital Subscriber
Line Asymmetric Digital Subscriber Line (ADSL) is a technology
allowing high rates of digital data to be sent over conventional
twisted-pair copper telephone lines. It is referred to as
asymmetric because it provides a significantly greater bandwidth in
one direction than the other, with faster data transfer from the
network to the subscriber than it is in the opposite direction.
Consequently, ADSL suits the Internet user who downloads large
amounts of data from the Net, but tends to send comparatively
little data back in return. Theoretically, data speeds of up to 9
Mbps (megabits per second) are possible downstream to the customer,
and up to 800 kbps (kilobits per second) upstream. This high-speed,
high bandwidth digital communication makes live MPEG2 video signals
possible, as well as a range of other multimedia broadband
services. However, in practice capacity is lower than the
theoretical maximum, because line length reduces data speed and
limits the exchange to subscriber distance at about 2 miles. ADSL
requires the installation of a special modem, but ADSL then
provides an 'always on' connection to subscribers. Simultaneous
voice and data transmission is also possible over the same line,
because the data transfer uses a section of the phone line
bandwidth not utilised by voice. Therefore, subscribers can leave
their computers logged onto the Net without interrupting their
normal phone connections. A form of ADSL, called Universal ADSL
(G.lite), has been approved as a standard by the ITU-TS for
services to homes and businesses. Universal ADSL can provide speeds
of up to 1.5 Mbps over conventional phone lines. However, although
a provider might typically offer a downstream rate of 512 kbps,
this is still about 10 times faster than the fastest
analogue-to-digital modems, and several times faster than an ISDN
(Integrated Services Digital Network) connection. Upstream speeds
can reach 128 kbps |
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Advanced Mobile Phone Service
: Also known as: AMPS Advanced Mobile Phone
Service (AMPS) is a first generation analogue cellular telephone
system that originated in the USA in the 1980s. AMPS is still the
most widely deployed cellular system in the United States, and has
been used in other countries of North and South America, as well as
the Asia/Pacific region, although it is not compatible with
European mobile phone standards. AMPS can be found in countries
such as Canada, Australia, Hong Kong, New Zealand, South Korea,
Singapore, Taiwan, Thailand and Israel. AMPS operates in the 800
and 900 MHz frequency bands. Frequency Division Multiple Access
(FDMA) is used to divide each band of operating frequencies into 30
kHz channels. Adjacent cells will then employ different channels
for their transmitted and received signals, so that one cell does
not interfere with another, and as a user moves between cells the
channels change without any noticeable transition. AMPS was updated
with digital cellular service, i.e. digital AMPS (DAMPS), by adding
Time Division Multiple Access (TDMA) to each channel |
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Adventure Game,
: A form of fictional simulation. These are
often set in fantasy worlds and involve decision making and
exploration. |
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