外文翻译2095683.docVIP

Data Transmission Data transmission is the conveyance of any kind of information from one spance to another. Historyically this could be done by a courier, a chain of bonfires and later by Morsec code over copper wires. In recent computer terms it means sending a stream bits or nytes from one location to another using any unmber of technologies ,such as copper wires optocal fiber laser radio or infra-red light. Prsactical examples include moving data from one storage device to another and accessing a website which involves sat transferr from web servers to a user’s browser. A related concept to data transmission is the data transmission protocol used to make the data transfer legible .Current protocols favor packet based communication. Types of data transmission Serial transmission :Bits are sent over a single wire indivdually. Whilst only one bit is sent at a time ,high transfer rates are possible. This can be used over longer distances as a check digit or parity bit can be sent along it easily. Parallel transmission :Multiple wires are usde to transmit bits simultaneously .It is much faster than seial transmission as one byte can be sent rather than one bit .This method is used internaly within the computer, for example the interal buses,and sometimes externally for such things as printers .however this method of transmission is only avvailable over shortdistances as the signal will degrade and become unreadable since there is more interference between many wires than within one. Asynchronous and synchronous data transmission Asynchronous transmission uses start and srop bits to signify the beginning and end of a transmission .This means thath an 8 bits ASCⅡ character would actually be transmitted using 10 bits,e.g.,A“1010000010”.The extra one (or zero depending on parity bit)at the start and end of transmission tells the receicer first that a character is coming and secondly that the character has ended ,This method of transmission us ysed when data is s