Monday, April 14, 2008

ADSL Modem

An ADSL modem is a device used to connect one or more computers to a phone line, in order to use an ADSL service. Some ADSL modems also manage the connection and sharing of the ADSL service with a group of machines, making an ADSL router or ADSL modem (router) a more accurate name for the device. ADSL modem acts as the ADSL Terminal Unit or ATU-R, as the telephone companies call it. The acronym NTBBA (Network Termination Broad Band Adapter, network termination broad band access) is also common in various countries.

ADSL modem vary in data speed from hundreds of Kilobits per second to many Megabits per second, while voiceband modems are limited to approximately 50 Kbit/s. ADSL modem exchanges data with only the DSLAM to which it is wired, which in turn connects it to the Internet, while most voiceband modems can dial directly anywhere in the world. Such modems are intended for particular protocols and sometimes won't work on another line even from the same company, while most voiceband modems use international standards and can "fall back" to find a standard that will work.

Most of these differences are of little interest to consumers, except the greater speed of ADSL and the ability to use the telephone even when the computer is online. This ability really puts them way ahead of many other modems which don't let you use telephone when connected to the internet.

As technology advances, functions that are provided by multiple chips can be integrated onto one chip. Higher levels of integration have benefitted ADSL modem just as they benefitted other computer hardware. Exactly what is on the circuit card and how it is arranged can change as technology improves but some of the essential components for its functionality include Transformer and capacitor for power supply, Data connection and power circuitry (for example, USB, Ethernet, PCI), DSL digital data pump, DSL analog chip and line driver, Microcontroller and a Filter.

Apart from connecting to an ADSL service, many modems offer additional integrated features. Many ADSL modems can have their firmware upgraded to support additional features or to fix existing problems. This can be done over the network, or by using a dedicated serial connection.

Currently, Taiwan manufactures most of the ADSL modems in the world, ODM plays a large role with designs from various parts of the world. The main manufacturing companies from Taiwan are Billion, D-Link, Draytek and ZyXEL. Another renowned manufacturer is 3COM which has its headquarters in USA.