HDSL The first development was the high bit-rate
HDSL The first development was the high bit-rate digital subscriber line (HDSL). It uses the same four-level phase amplitude modulation as ISDN (referred to as 2B1Q). By applying more sophisticated DSP technology and by using a wider bandwidth, HDSL can achieve the same, symmetric rates as T1 or E1 (1.5 or 2 Mbit/s) over a range of 12,000 ft using two pairs of 24 a.w.g. wire (3 km of 0.5 mm). This range is the Carrier Serving Area (CSA); that is, the area served by the local exchange carrier or telco (in the USA the RBOC), often using Digital Loop Carrier (DLC) technology. In many areas HDSL has replaced the original T-1, which required repeaters every few hundred yards. In Europe a variant of HDSL uses a single pair, but cannot achieve the same range. This is not a problem in countries like Germany and Italy, where the local loop tends to be shorter. All the HDSL systems are loop powered (no local power requirement at the subscriber end) and they use the analog voice band for data. ADSL Asymmetric DSL or ADSL is designed to allow the plain old telephone service (POTS) to be used at the same time as the digital service. This means that the line still can be used for voice or fax while data transfer is taking place. Frequency division multiplexing is used to separate the channels. The data occupies the spectrum from 25 kHz up to over 1 MHz, leaving the low-frequency baseband clear for the POTS. IP networks and telecommunications 33 3.4 kHz 25 kHz 1.1 MHz 0 voice fax ADSL frequency Figure 2.8 ADSL frequency multiplexing.
Note: If you are looking for good and high quality web space to host and run your application check Lunarwebhost Cheap Web Hosting services