ADSL (Asymmetrical Digital Subscriber Line)
ADSL is the most common form of DSL technology in the consumer space. It's faster in one direction, usually downstream to the client, while the upstream channel is slower. This is ideal for consumer use where traffic is typically download-heavy. It has a range from the exchange of around 5.5km.

ATM (Asynchronous Transfer Mode)
An ATM is a large, dedicated back-end connection used by telecommunications companies. It provides speeds from 155Mbps to 622Mbps.

Bandwidth
In analogue communications circles, bandwidth is the carrying capacity of a signal, and is the difference between the highest and lowest frequency, expressed in hertz. In digital communications it also refers to the amount of data that can pass over a connection, expressed in bits per second (bps).

Broadband
Traditionally defined in relation to narrowband and wideband, broadband represents any speeds above that of wideband, so either 1.544Mbps+ or 45Mbps+. These days broadband is a blanket term that refers to any connection with a speed above dial-up 56Kbps or a single 64Kbps ISDN connection.

Cable
Cable broadband refers to any connection made over fibre optic cable, instead of copper twisted pair. Telstra offers cable internet through the Foxtel cable. Optus and TransACT also offer cable internet services. Fibre optic cable has a much higher potential bandwidth than copper wire, and cable connections can run at speeds of up to 10Mbps. Typically, cable networks are designed for television, and don't have significant built-in capacity for an upstream channel, which means most cable services are asymmetric.

DSL (Digital Subscriber Line)
DSL is a technology that allows high speed data transfer over conventional twisted pair copper wire used for analogue voice lines. It makes use of frequencies above that used by the analogue telephony service, so it doesn't interfere with voice when in use. It requires specialised hardware on each end of the connection, namely a DSL modem at the client end, and a DSLAM at the exchange end. DSL comes in many different flavours with varying capacity and range.

DSLAM (Digital Subscriber Line Access Multiplexer)
The DSLAM is the device fitted to a telephone exchange that allows it to handle DSL connections over regular telephone lines. DSL works by splitting the bandwidth of the copper wire into discreet channels, each of which handle a data stream. The DSLAM then integrates these channels into a single data stream at the exchange.

DOCSIS (Data Over Cable Service Interface Specification)
An international standard for data communications over a television cable network. The first cable internet services used proprietary standards, but now both Telstra and Optus both use the DOCSIS standard.

E1
E1 is the European version of a T1 connection. It runs at 2.048Mbps and is used for both data and voice connections. It can be split up into 32 64Kbps channels, or bundled together to make one high speed connection.

HDSL (High bit rate Digital Subscriber Line)
HDSL is a very high speed variant of DSL technology, although the range is far more limited than with ADSL. HDSL can provide T1 or E1 speeds (1.544Mbps or 2.048Mbps respectively), at ranges of up to 12,000ft, or around 3.6km.

iBurst
iBurst is a new wireless broadband service that operates in a manner similar to conventional mobile phone access. It uses a number of specialised base stations that keep the user connected, even when travelling at high speeds. Current services offer 1Mbps, although the pricing is significantly higher than comparative fixed line broadband services. iBurst is currently available in Sydney through a number of ISPs, and will be expanding to include other major cities through 2004 and 2005.

ISDN (Integrated Services Digital Network)
ISDN is an international digital telephony standard that runs over normal copper wire. It can also be used for data, with a single channel able to handle 64Kbps. Multiple channels are usually bundled together to provide multiple low speed connections, or one higher speed connection.

Narrowband
The term narrowband is used in a number of different contexts, usually meaning a signal that only occupies a small range of the radio or electromagnetic spectrum. In the telecommunications world, it was typically defined in terms of ISDN or voice channels. Narrowband referred to anything with the bandwidth of a single 64Kbps voice channel, or less.

SDSL (Symmetric Digital Subscriber Line)
SDSL is a DSL connection that is the same speed upstream as downstream. This is ideal for businesses where outgoing traffic is just as heavy as incoming, such as when hosting a website or connecting to a remote office with a VPN. SDSL has a maximum range from the exchange of 11,000ft, or around 3.3km.

V.90
V.90 is the most popular analogue modem standard used in Australia. It combines two earlier 56K standards, K56Flex and x2 into one protocol. It allows speeds of up to 56Kbps downstream and 33.6Kbps upstream.

V.92
V.92 is a new analogue modem standard that supersedes the V.90 standard. It incorporates a number of new features, such as Modem-on-hold, which allows the modem to suspend the internet connection when a voice call comes in, then resume the connection when the voice call has ended. It also remembers the previous connection settings, allowing the modem to perform the handshake faster. The upstream channel has also been increased to a maximum of 48Kbps. Only some ISPs support these features, so you should confirm before purchasing a V.92 modem.

Wideband
Wideband is a term that is little used these days, but is variously defined as any connection with a bandwidth of between 64Kbps (or a single ISDN voice channel) and 1.544Mbps (24 ISDN channels, or a T1 connection in the US). It is also sometimes defined as any connection between 1.544Mbps and 45Mbps in general digital communication circles.