page_title: Modem
section_title: Broadband
hierarchical_section_title: Modem / Broadband
caption_attribution_description: English: ARRIS CM820B DOCSIS Cable Modem "DS" and "US" stand for "Downstream" and "Upstream" respectively. "Link" (Ethernet) light is yellow for 100 Mbit/s and green for 1000 Mbit/s.
context_page_description: A modem – a portmanteau of "modulator-demodulator" – is a hardware device that converts data from a digital format, intended for communication directly between devices with specialized wiring, into one suitable for a transmission medium such as telephone lines or radio. A modem modulates one or more carrier wave signals to encode digital information for transmission, and demodulates signals to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded reliably to reproduce the original digital data.
  Modems can be used with almost any means of transmitting analog signals, from light-emitting diodes to radio. A common type of modem is one that turns the digital data of a computer into a modulated electrical signal for transmission over telephone lines, to be demodulated by another modem at the receiver side to recover the digital data.
context_section_description: The term broadband gained widespread adoption in the late 90s to describe internet access technology exceeding the 56 kilobit/s maximum of dialup. There are many broadband technologies, such as various DSL (Digital Subscriber Line) technologies and cable broadband. 
  DSL technologies such as ADSL, HDSL and VDSL use telephone lines (wires that were installed by a telephone company and originally intended for use by a telephone subscriber) but do not utilize most of the rest of the telephone system. Their signals are not sent through ordinary phone exchanges, but are instead received by special equipment (a DSLAM) at the telephone company central office. 
  Because the signal does not pass through the telephone exchange, no "dialing" is required, and the bandwidth constraints of an ordinary voice call are not imposed. This allows much higher frequencies, and therefore much faster speeds. ADSL in particular is designed to permit voice calls and data usage over the same line simultaneously. 
  Similarly, cable modems use infrastructure originally intended to carry television signals, and like DSL, typically permit receiving television signals at the same time as broadband internet service. 
  Other broadband modems include satellite modems and power line modems.
caption: Cable modem
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