ADSL
'Asymmetrical Digital Subscriber Line'; the most common form of broadband access transmitted over telephone lines and made possible by upgrading telephone exchanges. By being asymmetrical, it exploits the one-way nature of most multimedia communication in which large amounts of information flow toward the user and only a small amount of interactive control information is returned. Bandwidth
A measure of how much electronic data can be carried in a given time period i.e. speed. The greater your speed of connection to the Internet, the greater your 'bandwidth'. Activities that require access to the Internet such as business applications, file downloads or multimedia streaming are typically referred to as requiring high 'bandwidth'.
Broadband
A high speed digital internet connection which features bandwidth in excess of 512 Kbps and is 'always on'.
Cable Broadband
A high capacity coaxial cable 'built-out' to individual homes and businesses by cable companies, though typically only in metropolitan areas. The use of a cable modem allows users to access the Internet, as well as premium TV channels.
Dial Up - Internet
Dial-up internet access which is made by initiating a telephone call. A dial-up connection is established and maintained for a limited time duration and will achieve only a limited, transfer of data (to a maximum of around 56 Kbps).
DSLAM
Digital Subscriber Line Access Multiplexer. This is the device installed in the telephone exchange connecting ADSL circuits to the BT network.
IP
IP or Internet Protocol is the way in which data is sent between computers on the Internet. If you want to send or receive data then it is divided into smaller pieces, known as IP 'packets'. Each 'packet' contains the sender and receiver's addresses and they are forwarded by a chain of gateway computers until they reach their destination.
ISDN
Integrated Services Digital Network. ISDN usually offers maximum connection speeds of 128Kbps. The technology is widely available in many areas, though it is rapidly becoming less popular as Broadband equivalents become relatively cheaper.
ISP
An Internet Service Provider, i.e. a company which provides Internet access.
Mbps & Kbps
A measurement of the amount of electronic information which is transferred over an internet connection. 1Mbps is one Megabit (a million bits) per second, while 1Kbps is one Kilobit (a thousand) per second.
Microfilter
Devices which need to be plugged into all existing telephone and extension sockets to ensure that the ADSL signal on the telephone line does not interfere with voice calls.
Modem
Acronym derived from mo dulator/ dem odulator, a modem is a device for connecting computers via the internet.
PSTN
The global collection of interconnected, voice-orientated public telephone networks, both government and commercially owned, is known as the Public Switched Telephone Network.
Satellite Broadband
A high bandwidth method of broadband access used mostly in rural areas where other access methods are unavailable or unviable. It operates on the same principles as satellite TV.
SDSL
'Symmetrical Digital Subscriber Line'; a form of broadband connection used to transmit high-bandwidth information over ordinary telephone lines into homes and small businesses. With SDSL the data rate is the same in both directions (upstream and downstream) hence its symmetry. For this reason the technology is preferable to ADSL equivalents - particularly among business users.
Upstream / Downstream
This refers to the transmission of data. If data travels from the end user to the information server then it is travelling upstream and if the transmission of data is from an information server to the end user then the direction it is travelling in is downstream. For example. ADSL is well suited to web browsing as it enables high bandwidth downstream, but comparatively narrow bandwidth upstream.
VPN
Virtual Private Network is a method of using the Internet, to give individual users or remote offices secure access to their company's network.
Wireless Broadband
Technology enabling users within a locality to access the Internet via radio frequencies. Offered mainly by specialist service providers, wireless broadband is ideal for subscribers in remote areas as they can be brought into the network without the need for new cabling/wiring across the countryside.
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