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Asymmetric Digital Subscriber Line - technical term describing the particular technology used to deliver Broadband using your existing telephone cables. ADSL provides download speeds of up to 8Mbit/s and upload speeds of up to 1Mbit/s per second. The different downstream and upstream rates defines the Asymmetry.

Typical service offering from Internet Service Providers (ISP) limits the available bandwidth to 0.5Mbit/s (500kbit/s) in order to limit network costs and therefore provide the most cost effective solution for the Subscriber.

The download speeds of 10-200 times that of normal dial-up internet access, enables new applications such as file sharing, on-line gaming, video-conferencing, and real time audio and video streaming at acceptable quality.

The little gizmo that has enabled self-installable ADSL service. Sometimes also called a Micro Filter or Distributed Filter, we prefer ADSL Filter.

The filter actually blocks the ADSL signal on your telephone line from reaching your telephone handset. This ensures that no audible interference reaches your telephony device. Without a filter you may hear varying degress of hiss/noise on the line.

You should fit an ADSL filter in between the wall socket and EVERY telephony device that shares the telephone line. This will include: All telephone handsets, dial-up modems, fax machines, burglar alarms, AND don't forget your Satellite Receiver/Set-top box !!

Always-on is the marketing term widely used to compare and describe ADSL service with traditional dial-up modems. ADSL service is more accurately described as "always-available", as the dial-in concept is still used to connect to your ISP, however, the speed of connection and the flat-rate charging used by most ISPs, gives ADSL service the flavour of "always-on".

In addition the ability to use a telephone on the same line as the ADSL service combined with the ability to leave an ADSL session permanently connected, further adds to the flavour of "always-on"

The term bandwidth refers to the configured speed of your ADSL line. It is analogous to the size of a water pipe. The bigger the pipe the more water that can flow. Similarly the larger the bandwidth the greater the data transfer rate.

It of course is worth mentioning that the end-end connection speed, that figure shown in the corner of your browser, will vary greatly from your ISP's ADSL service bandwidth, as the data rate will be limited by the lowest bandwidth connection between your ISP and the content provider

Internet Service Provider. These are the folk from whom you purchase your ADSL/Broadband service. They in turn purchase the network connectivity between you and your local exchange from Karoo.

Early installations of ADSL, used Karoo network engineers to install the complete end-end service on behalf of the ISP. This often confused Subscribers as to who actually provides the service. Thankfully this is a dying art, now that self-install ADSL service is available.

In the contect of ADSL service, is the time taken for data to get from your computer to the destination (and likewise from the content provider to your computer - so called "round-trip delay"). Latency is often discussed because ADSL often adds a significant contribution to the overall round-trip delay time.

The inherent delay in ADSL is due to the error correction techniques used to ensure that data travelling the 5km from your home to the exchange (and back) arrives intact. Simply, the more error correction that is added, the longer the delay, so a trade-off is used, as is the case with Karoo's service.

Other factors that affect the latency or delay, are the speed of the ADSL connection (particularly upstream, so if you have a rate-adaptive ADSL service, and you live close to the exchange you should have a lower latency), the type of ADSL modem or router used, and the speed of the network connection provided by your ISP.

Latency is more of an issue for real-time applications such as video-conferencing and gaming. Gamers in particular will seek out an ADSL router as their preferred choice of equipment as a router does not relay on the computer to perform some of the functions it would perform when using a USB or PCI modem.

Whilst the term modem actually stands for modulator/demodulator, the term can be used to refer to any piece of ADSL cusomer equipment. More likely the term is used to refer to a PCI or USB device that has no routing functionality built in. In this way ADSL modems are differentiated from ADSL routers.

It is worth noting that several products on the market referred to as "ADSL Routers" do not actually connect directly to your ADSL / telephone line, and are infact simply routers that can be connected to a separate ADSL modem. More prevalent in the USA, where early ADSL adopters had no choice but to purchase an ADSL modem plus a separate router, some UK customers have been caught out. Always check with your ADSL equipment supplier that your ADSL routers actually includes the ADSL modem.

In ADSL circles a router will be a product that combines an ADSL modem, for direct connection to an ADSL enabled phone line, with a multi device IP routing capability, for the connection of multiple devices to a single ADSL connection.

Routers provide varying degrees of functionality and care should be taken when choosing an ADSL router that it will perform the functions that you need. These will largely be influenced by the IP addressing scheme you are using and the type of devices you want to connect to ADSL (e.g. mail servers). Almost certainly you will need a device that provides Network and Port Address Translation, DHCP server and Firewall features. For connection to an existing router or Firewall, a router supporting DHCP spoofing is often ideal.

The new wave of ADSL subscribers will almost certainly make use of self-install products from their chosen ISP. This important development helps in reducing the start-up costs of ADSL, as there is no longer a need for a Karoo engineer to come and pay you a visit. All that is needed is for the Karoo man to wire your telephone line to the ADSL equipment at your local telephone exchange.

The breakthrough in providing UK customers with the ability to self-install came with the availability of a suitable ADSL Micro-Filter for use on Karoo's telephone lines. The SpeedTouch (Excelsus) Filter is the first filter that meets the requirements laid down by Karoo for such a device.