Modems
Peripherals consumer modems product pcba motherboards assembly electronics contract manufacturing services OEM CEM EMS experience company—China Shenzhen TopscomADSL (asymmetric digital subscriber line) modems, a more recent development, are not limited to the tele's voiceband audio frequencies. Early proprietary ADSL modems used carrierless amplitude phase (CAP) modulation. All standardized asymmetric DSL variants, including ANSI T1.413 Issue 2, G.dmt, ADSL2, ADSL2+, VDSL2, and G.fast, use discrete multi-tone (DMT) modulation, also called (coded) orthogonal frequency-division multiplexing (OFDM or COFDM).Standard twisted-pair tele cable can, for short distances, carry signals with much higher frequencies than the cable's maximum frequency rating. ADSL broadband takes advantage of this capability. However, ADSL's performance gradually declines as the tele cable's length increases. This limits ADSL broadband service to subscribers within a relatively short distance from the tele exchange.Cable modems use a range of radio frequencies originally intended to carry television signals. A single cable can carry radio and television signals at the same time as broadband internet service without interference. Multiple cable modems attached to a single cable can use the same frequency band by employing a low-level media access protocol to avoid conflicts. In the prevalent DOCSIS system, frequency-division duplexing (FDD) separates uplink and downlink signals. For a single-cable distribution system, the return signals from customers require bidirectional amplifiers or reverse path amplifiers that send specific customer frequency bands upstream to the cable plant amongst the downstream frequency bands. Newer types of broadband modems are available, including satellite and power line modems. Most consumers did not know about networking and routers when broadband became available. However, many people knew that a modem connected a computer to the Internet over a tele line. To take advantage of consumers' familiarity with modems, companies called these devices broadband modems rather than using less familiar terms such as adapter, interface, transceiver, or bridge. In fact, broadband modems fit the definition of modem because they use complex waveforms to carry digital data. They use more advanced technology than dial-up modems: typically they can modulate and demodulate hundreds of channels simultaneously or use much wider channels than dial-up modems.Topscom Technology is one of the leading manufacturers and suppliers who is committed to provide customers high quality and customized modems. Our factory can also give you wholesale service which is made in China, welcome to get modems with us.
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