A 13-year-old Chinese native has looked after his blind parents

In radio, for example, a very narrow band will carry Morse code, a broader band will carry speech, and a still broader band will carry music without losing the high audio frequencies required for realistic sound reproduction. This broad band is often divided into channels or "frequency bins" using passband techniques to allow frequency-division multiplexing instead of sending a higher-quality signal. A television antenna may be described as "broadband" because it is capable of receiving a wide range of channels, while a single-frequency or Lo-VHF antenna is "narrowband" since it receives only 1 to 5 channels. The U.S. federal standard FS-1037C defines "broadband" as a synonym for wideband.[3] In data communications a 56k modem will transmit a data rate of 56 kilobits per second (kbit/s) over a 4-kilohertz-wide telephone line (narrowband or voiceband). The various forms of digital subscriber line (DSL) services are broadband in the sense that digital information is sent over multiple channels. Each channel is at higher frequency than the baseband voice channel, so it can support plain old telephone service on a single pair of wires at the same time.[4] However, when that same line is converted to a non-loaded twisted-pair wire (no telephone filters), it becomes hundreds of kilohertz wide (broadband) and can carry up to 60 megabits per second using very-high-bitrate digital subscriber line (VDSL or VHDSL) techniques. In the late 1980s, the Broadband Integrated Services Digital Network (B-ISDN) used the term to refer to a broad range of bit rates, independent of physical modulation details.[5] In computer networks[edit] Many computer networks use a simple line code to transmit one type of signal using a medium's full bandwidth using its baseband (from zero through the highest frequency needed). Most versions of the popular Ethernet family are given names such as the original 1980s 10BASE5 to indicate this. Networks that use cable modems on standard cable television infrastructure are called broadband to indicate the wide range of frequencies that can include multiple data users as well as traditional television channels on the same cable. Broadband systems usually use a different radio frequency modulated by the data signal for each band.[6] The total bandwidth of the medium is larger than the bandwidth of any channel.[7] The 10BROAD36 broadband variant of Ethernet was standardized by 1985, but was not commercially successful.[8][9] The DOCSIS standard became available to consumers in the late 1990s, to provide Internet access to cable television residential customers. Matters were further confused by the fact that the 10PASS-TS standard for Ethernet ratified in 2008 used DSL technology, and both cable and DSL modems often have Ethernet connectors on them. Power lines have also been used for various types of data communication. Although some systems for remote control are based on narrowband signaling, modern high-speed systems use broadband signaling to achieve very high data rates. One example is the ITU-T G.hn standard, which provides a way to create a local area network up to 1 Gigabit/s (which is considered high-speed as of 2014) using existing home wiring (including power lines, but also phone lines and coaxial cables). In video[edit] "Broadband" in analog video distribution is traditionally used to refer to systems such as cable television, where the individual channels are modulated on carriers at fixed frequencies.[10] In this context, baseband is the term's antonym, referring to a single channel of analog video, typically in composite form with separate baseband audio.[11] The act of demodulating converts broadband video to baseband video. Fiber optic allows the signal to be transmitted farther without being repeated. Cable companies use a hybrid system using fiber to transmit the signal to neighborhoods and then changes the signal from light to radio frequency to be transmitted to over coaxial cable to homes. Doing so reduces the use of having multiple head ends. A head end gathers all the information from the local cable networks and movie channels and then feeds the information into the system

SHARE

About Unknown