For businesses, data communications have become vital to success in the marketplace, particularly with the increasing trend toward globalization. Communications networks allow both individuals and teams to communicate faster and better, obviate the need for many in-person meetings, and even transfer funds electronically. Through local, metropolitan, or wide area networks, individual computers or workstations can be linked together to enable data sharing and communication.
Next Topic TOC The distance over which data moves within a computer may vary from a few thousandths of an inch, as is the case within a single IC chip, to as much as several feet along the backplane of the main circuit board. Over such small distances, digital data may be transmitted as direct, two-level electrical signals Data communications system essay simple copper conductors.
Except for the fastest computers, circuit designers are not very concerned about the shape of the conductor or the analog characteristics of signal transmission. Frequently, however, data must be sent beyond the local circuitry that constitutes a computer.
In many cases, the distances involved may be enormous. Unfortunately, as the distance between the source of a message and its destination increases, accurate transmission becomes increasingly difficult.
This results from the electrical distortion of signals traveling through long conductors, and from noise added to the signal as it propagates through a transmission medium. In this case, distortion and noise can become so severe that information is lost.
Data Communications concerns the transmission of digital messages to devices external to the message source. As a rule, the maximum permissible transmission rate of a message is directly proportional to signal power, and inversely proportional to channel noise.
It is the aim of any communications system to provide the highest possible transmission rate at the lowest possible power and with the least possible noise.
It may be defined by a physical wire that connects communicating devices, or by a radio, laser, or other radiated energy source that has no obvious physical presence.
Information sent through a communications channel has a source from which the information originates, and a destination to which the information is delivered. Although information originates from a single source, there may be more than one destination, depending upon how many receive stations are linked to the channel and how much energy the transmitted signal possesses.
In a digital communications channel, the information is represented by individual data bits, which may be encapsulated into multibit message units. A byte, which consists of eight bits, is an example of a message unit that may be conveyed through a digital communications channel.
A collection of bytes may itself be grouped into a frame or other higher-level message unit.
Such multiple levels of encapsulation facilitate the handling of messages in a complex data communications network. Any communications channel has a direction associated with it: The message source is the transmitter, and the destination is the receiver.
A channel whose direction of transmission is unchanging is referred to as a simplex channel. For example, a radio station is a simplex channel because it always transmits the signal to its listeners and never allows them to transmit back.
A half-duplex channel is a single physical channel in which the direction may be reversed.
Messages may flow in two directions, but never at the same time, in a half-duplex system. In a telephone call, one party speaks while the other listens.
After a pause, the other party speaks and the first party listens. Speaking simultaneously results in garbled sound that cannot be understood.
A full-duplex channel allows simultaneous message exchange in both directions. It really consists of two simplex channels, a forward channel and a reverse channel, linking the same points.
The transmission rate of the reverse channel may be slower if it is used only for flow control of the forward channel. Because it is neither practical nor economic to transfer all bits of a long message simultaneously, the message is broken into smaller parts and transmitted sequentially.
Bit-serial transmission conveys a message one bit at a time through a channel. Each bit represents a part of the message. The individual bits are then reassembled at the destination to compose the message.
In general, one channel will pass only one bit at a time. Thus, bit-serial transmission is necessary in data communications if only a single channel is available.
Bit-serial transmission is normally just called serial transmission and is the chosen communications method in many computer peripherals. Byte-serial transmission conveys eight bits at a time through eight parallel channels.
Although the raw transfer rate is eight times faster than in bit-serial transmission, eight channels are needed, and the cost may be as much as eight times higher to transmit the message. When distances are short, it may nonetheless be both feasible and economic to use parallel channels in return for high data rates.
The popular Centronics printer interface is a case where byte-serial transmission is used. As another example, it is common practice to use a bit-wide data bus to transfer data between a microprocessor and memory chips; this provides the equivalent of 16 parallel channels.- Communications Technology Your Rights and what the Data Protection Commissioner can do to help Right of Access The personal information to which you are entitled is that held on computer or in a manual filing system that .
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A popup is a type of window that appears on top of (over) the browser window of a Web site that a user has visited. In contrast to a pop-under ad, which appears behind (in back of) the browser window, a popup is more obtrusive as it covers other windows, particularly the window that the user is trying to read.
Determining Databases and Data Communications BIS University of Phoenix Instructor: Cornell Perry In this paper the writer will seek to respond to the questions designated for both scenarios.
This paper will list typical fields for each type of caninariojana.come an example of two relationships that you need to track. This paper will . What Is Data Communication Systems Technology? If you worked in data communication systems technology, you would design and execute the structures that allow information to be transferred from computer to computer or across voice and data networks.
Degree programs for data communications specialists include information .
Information technology (IT) is the use of computers to store, retrieve, transmit, and manipulate data, or information, often in the context of a business or other enterprise.
IT is considered to be a subset of information and communications technology (ICT).. Humans have been storing, retrieving, manipulating, and communicating information since the Sumerians in Mesopotamia developed writing.