What is a DSL modem?
A DSL modem is a device that is used to connect a computer or router to a telephone circuit that has a Digital Service Line (DSL). Using a Digital Subscriber Line Access Multiplexer (DSLAM), the DSL modem modulates high-frequency tones for transmission. The DSL modem will also receive and demodulate the transmissions from the DSLAM. Compared to analog dial-up, DSL significantly increases the bandwidth between the user's computer and the Internet. Download speeds are theoretically capable of reaching 10 Mbps and beyond, but telephone companies often limit the speed and/or bandwidth capabilities to prevent Web Hosting. However, DSL modems still transfer data at a rate which is typically 10 to 20 times that of a voice-band modem. Furthermore, a single telephone line can be used for simultaneous voice and data with DSL, while a voice-band modem does not allow for simultaneous voice traffic. Because a single phone line commonly carries DSL and voice, DSL filters are used to separate the two lines. DSL modems use frequencies from 25 kHz - 1MHz, in order not to interfere with voice service (which is primarily located between 0-4kHz. Some DSL modems also manage the connection for and sharing of the DSL service in a network, and in this case, the DSL modem would be referenced as a DSL router or residential gateway.Most DSL modems are external to the computer and wired to the computer's Ethernet port. Less common are DSL modems that connect to a computers USB port. Internal DSL modems with PCI interfaces are also available, however, they too are rare compared to DSL modems that use an Ethernet port. Like many other computer technologies, DSL functions that have typically been provided by multiple chips can be integrated onto one chip.
Various Manufactures of DSL modems
- NetGear
- Motorola
- TRENDnet
- Linksys
- Zoom
- Cisco
- Siemens
- D-Link
- Actiontec
- Qwest
Shantanu
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