Data transmission - Wikipedia, the free encyclopedia. Data transmission, digital transmission or digital communications is the physical transfer of data (a digitalbit stream or a digitized analog signal[1]) over a point- to- point or point- to- multipoint communicationchannel. Examples of such channels are copper wires, optical fibers, wireless communication channels, storage media and computer buses. The data are represented as an electromagneticsignal, such as an electrical voltage, radiowave, microwave, or infrared signal. While analog transmission is the transfer of a continuously varying analog signal over an analog channel, digital communications is the transfer of discrete messages over a digital or an analog channel. The messages are either represented by a sequence of pulses by means of a line code (baseband transmission), or by a limited set of continuously varying wave forms (passband transmission), using a digital modulation method. The passband modulation and corresponding demodulation (also known as detection) is carried out by modem equipment. According to the most common definition of digital signal, both baseband and passband signals representing bit- streams are considered as digital transmission, while an alternative definition only considers the baseband signal as digital, and passband transmission of digital data as a form of digital- to- analog conversion. Data transmitted may be digital messages originating from a data source, for example a computer or a keyboard. It may also be an analog signal such as a phone call or a video signal, digitized into a bit- stream for example using pulse- code modulation (PCM) or more advanced source coding (analog- to- digital conversion and data compression) schemes. This source coding and decoding is carried out by codec equipment. Distinction between related subjects[edit]Courses and textbooks in the field of data transmission[1] as well as digital transmission[2][3] and digital communications[4][5] have similar content. Digital transmission or data transmission traditionally belongs to telecommunications and electrical engineering. Basic principles of data transmission may also be covered within the computer science/computer engineering topic of data communications, which also includes computer networking or computer communication applications and networking protocols, for example routing, switching and inter- process communication. Convert your PDF files to Word, Excel, PowerPoint and more. Convert various formats to PDF. Store & share your documents for free. Cometdocs prides itself on providing the best document conversion in the business. Learn more ยป. Although the Transmission control protocol (TCP) involves the term "transmission", TCP and other transport layer protocols are typically not discussed in a textbook or course about data transmission, but in computer networking. The term tele transmission involves the analog as well as digital communication. In most textbooks, the term analog transmission only refers to the transmission of an analog message signal (without digitization) by means of an analog signal, either as a non- modulated baseband signal, or as a passband signal using an analog modulation method such as AM or FM. It may also include analog- over- analog pulse modulatated baseband signals such as pulse- width modulation. In a few books within the computer networking tradition, "analog transmission" also refers to passband transmission of bit- streams using digital modulation methods such as FSK, PSK and ASK. Note that these methods are covered in textbooks named digital transmission or data transmission, for example.[1]The theoretical aspects of data transmission are covered by information theory and coding theory. Protocol layers and sub- topics[edit]Courses and textbooks in the field of data transmission typically deal with the following OSI model protocol layers and topics: Applications and history[edit]Data (mainly but not exclusively informational) has been sent via non- electronic (e. Analog signal data has been sent electronically since the advent of the telephone. Free file and disk utilities, backup programs, file splitters, zip programs, disk search programs, data wiping tools, etc.![]() However, the first data electromagnetic transmission applications in modern time were telegraphy (1. The fundamental theoretical work in data transmission and information theory by Harry Nyquist, Ralph Hartley, Claude Shannon and others during the early 2. Data transmission is utilized in computers in computer buses and for communication with peripheral equipment via parallel ports and serial ports such as RS- 2. Firewire (1. 99. 5) and USB (1. The principles of data transmission are also utilized in storage media for Error detection and correction since 1. Data transmission is utilized in computer networking equipment such as modems (1. LAN) adapters (1. In telephone networks, digital communication is utilized for transferring many phone calls over the same copper cable or fiber cable by means of Pulse code modulation (PCM), i. Time division multiplexing (TDM) (1. Telephone exchanges have become digital and software controlled, facilitating many value added services. For example, the first AXE telephone exchange was presented in 1. Since the late 1. Integrated Services Digital Network (ISDN) services. Since the end of the 1. ADSL, Cable modems, fiber- to- the- building (FTTB) and fiber- to- the- home (FTTH) have become widespread to small offices and homes. The current tendency is to replace traditional telecommunication services by packet mode communication such as IP telephony and IPTV. Transmitting analog signals digitally allows for greater signal processing capability. The easiest way to send large files fast.and it's Free! Create an Account Login. Or check out the features tour. Citrix ShareFile is the secure file sharing and transfer service that's built for business. Share files with clients and colleagues professionally. Try it Free! Courses and textbooks in the field of data transmission typically deal with the following OSI model protocol layers and topics: Layer 1, the physical layer: Channel coding including Digital modulation schemes; Line coding. The ability to process a communications signal means that errors caused by random processes can be detected and corrected. Digital signals can also be sampled instead of continuously monitored. The multiplexing of multiple digital signals is much simpler to the multiplexing of analog signals. Because of all these advantages, and because recent advances in widebandcommunication channels and solid- state electronics have allowed scientists to fully realize these advantages, digital communications has grown quickly. Digital communications is quickly edging out analog communication because of the vast demand to transmit computer data and the ability of digital communications to do so. The digital revolution has also resulted in many digital telecommunication applications where the principles of data transmission are applied. Examples are second- generation (1. TV (1. 99. 8), digital radio (1. Data transmission, digital transmission or digital communications is the physical transfer of data (a digital bit stream or a digitized analog signal[1]) over a point- to- point or point- to- multipoint communication channel. Examples of such channels are copper wires, optical fibers, wireless communication channels, storage media and computer buses. The data are represented as an electromagnetic signal, such as an electrical voltage, radiowave, microwave, or infrared signal. While analog transmission is the transfer of a continuously varying analog signal over an analog channel, digital communications is the transfer of discrete messages over a digital or an analog channel. The messages are either represented by a sequence of pulses by means of a line code (baseband transmission), or by a limited set of continuously varying wave forms (passband transmission), using a digital modulation method. The passband modulation and corresponding demodulation (also known as detection) is carried out by modem equipment. According to the most common definition of digital signal, both baseband and passband signals representing bit- streams are considered as digital transmission, while an alternative definition only considers the baseband signal as digital, and passband transmission of digital data as a form of digital- to- analog conversion. Data transmitted may be digital messages originating from a data source, for example a computer or a keyboard. It may also be an analog signal such as a phone call or a video signal, digitized into a bit- stream for example using pulse- code modulation (PCM) or more advanced source coding (analog- to- digital conversion and data compression) schemes. This source coding and decoding is carried out by codec equipment. Serial and parallel transmission[edit]In telecommunications, serial transmission is the sequential transmission of signal elements of a group representing a character or other entity of data. Digital serial transmissions are bits sent over a single wire, frequency or optical path sequentially. Because it requires less signal processing and less chances for error than parallel transmission, the transfer rate of each individual path may be faster. This can be used over longer distances as a check digit or parity bit can be sent along it easily. In telecommunications, parallel transmission is the simultaneous transmission of the signal elements of a character or other entity of data. In digital communications, parallel transmission is the simultaneous transmission of related signal elements over two or more separate paths. Multiple electrical wires are used which can transmit multiple bits simultaneously, which allows for higher data transfer rates than can be achieved with serial transmission. This method is used internally within the computer, for example the internal buses, and sometimes externally for such things as printers, The major issue with this is "skewing" because the wires in parallel data transmission have slightly different properties (not intentionally) so some bits may arrive before others, which may corrupt the message. A parity bit can help to reduce this. However, electrical wire parallel data transmission is therefore less reliable for long distances because corrupt transmissions are far more likely. Types of communication channels[edit]Asynchronous and synchronous data transmission[edit]Asynchronous start- stop transmission uses start and stop bits to signify the beginning bit[citation needed]ASCII character would actually be transmitted using 1. For example, "0. 10. 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