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China Electronics Ems Manufacturer
May 19, 2017

Telecommunication network telcommunication Dsl optical egpon Modems  pcba motherboards assembly electronics contract manufacturing services OEM CEM EMS experience company—China Shenzhen Topscom
A modem (modulator-demodulator) is a network hardware device that 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 to reproduce the original digital data. Modems can be used with 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 modulated electrical signal for transmission over telephone lines and demodulated by another modem at the receiver side to recover the digital data.

Modems are generally classified by the amount of data they can send in a given unit of time, usually expressed in bits per second (symbol bit/s, sometimes abbreviated "bps"), or bytes per second (symbol B/s). Modems can also be classified by their symbol rate, measured in baud. The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal. For example, the ITU V.21 standard used audio frequency shift keying with two possible frequencies, corresponding to two distinct symbols (or one bit per symbol), to carry 300 bits per second using 300 baud. By contrast, the original ITU V.22 standard, which could transmit and receive four distinct symbols (two bits per symbol), transmitted 1,200 bits by sending 600 symbols per second (600 baud) using phase shift keying.

56 kbit/s line
Automatic negotiation (or handshake)
BBN Technologies (developed the first model in 1963)
Broadband: satellite modem, ADSL, cablemodem, PLC
Command and Data modes (modem)
Device driver
Fax demodulator
Internet outdial
ITU V-series telephone network modem standards, including V.92
List of device bandwidths
Plug and play
RJ-11 (TelCo Interface Port Model Number)
Router (computing)
Rockwell (Chipset)
X2 (Chipset)
List of modem standards