ADSL stands for Asymmetric Digital Subscriber Line. This technology allows you to use the whole bandwidth of a standard telephone copper cabling.
While the POTS ( Plain Old Telephone Service ) uses the frequencies between 300 and 3100Hz, the higher frequencies normally remain unused. ADSL uses the frequencies between 30KHz and 1.1MHz to transport data, leaving your telephone connection, like crystal and pure as ever.
ADSL can be easily and seamlessly combined with the existing ISDN lines — so no need to worry, if you already have one.
Q1. What is ADSL?
A1. ADSL is the abbreviation for Asymmetric Digital Subscriber Line. This technology allows us to use the remaining bandwidth of a standard telephone copper cabling. While the POTS ( Plain Old Telephone Service ) uses the frequencies between 300 and 3100Hz, the higher frequencies normally remain unused. ADSL uses the frequencies between 30KHz and 1.1MHz to transport data, e.g., digital data.
Q2. Why asymmetric?
A2: A typical residential user downloads more (e.g., surfing to a website) than uploads to the Internet (e.g., sending a mail). It is, therefore, better to divide the available capacity of the line asymmetrically.
Q3. How fast is ADSL?
A3. The theoretical limits are 1 Mbits/s for upload, 8 Mbits/s for download. The real speed you’ll get depends on a lot of factors: the contract with your ADSL Operator/ISP, the interface between the modem ( Ethernet, USB… ) and your computer settings and capabilities, what software package you are using and the distance to the exchange.
Q4. What ADSL standards are supported by the SpeedTouch modems?
A4. SpeedTouch modems support the following ADSL standards:
- G.992.1 (G.dmt) standards information and G.992.2 (G.lite) standards information
- Full Rate ANSI TI.413-issue2
- ETSI TS 101 388( ISDN)
- ITU-G Handshake (Automode ITU G.994.1)
Q5. Does ADSL interfere with the usual telephone service? Can I still use my normal modem?
A5. ADSL works on totally different frequencies than the classic telephone services, and as such, the two can be used at the same time. The only limitation is that the user will need filters to avoid interferences between the two services. A classic modem can still be used to allow small-band connectivity to the Internet or to send faxes.
Q6. Can I fax with my ADSL modem?
A6. ADSL uses other frequencies than the classic telephone services. If you wish to use Internet services to send a fax, you may do so through your ADSL connection. Otherwise, you’ll need a normal modem of telefax machine to send faxes the classic way.
Q7. Can I use ADSL on my ISDN line?
A7. Yes, the ADSL technology has been adapted to be used over an ISDN ( digital ) line. Because the ISDN uses more bandwidth than the normal POTS services, there will be fewer frequencies available for ADSL, which means the theoretical speed limit of ADSL will be lower over ISDN than over a normal line. Usually, the end-user won’t feel the difference.
Q8. What are the differences between the many xDSL variations?
A8. The most used variations are:
ADSL: Asymmetric Digital Subscriber Line: different line rates for upstream and downstream, typically, 8Mbits/s downstream, 1 Mbit/s upstream
SDSL or SHDSL: Symmetric/High bit-rate DSL: same line rates for upstream and downstream, typically around 2Mbits/s.
VDSL: Very high data transfer speed rate DSL is being developed. It will offer up to 55Mbits/s on shorter distances ( +/- 1000 feet or 300 meters ).