Monday, November 19, 2012

Type of Transmission

              Type of information or data signal transmission in a medium can be grouped into two parts, namely the transmission of parallel and serial transmission.
  1.         Parallel Transmission
              In parallel transmission, a connector consisting of seven or eight bits (ASCII) transmitted simultaneously at any time. For example, if use ASCII code, it is necessary to transmit as many as eight lanes as well as 8 bit ASCII code for a single character. Display parallel transmission can be seen in this picture.
              In parallel transmission is transmitted in parallel is the bits that represent a single character, while each character transmitted serially. Parallel communication is used for short distance communication, the transmission of this type normally used to transmit signals inside a computer or between computers to the printer. Examples of this type of communication is a DB-25 parallel.
            Shipping with parallel transmission mode has high speed, because every moment can be directly transmitted one character. However, this transmission mode requires a special cable that consists of several paths to be used in delivery of the bits of the character.

2.         SerialTransmission
Serial transmission is a form of transmission that are commonly used. In serial  transmission, the individual bits of a character are sent sequentially, ie bit by bit, in which one bit followed by the next bit. In this system the receiver will collect the number of bits (for the system ASCII = 8 bits) are sent by the transmitter to then be used as a single character.
Serial transmission can be grouped in three forms, namely Synchronous Transmission, Asynchronous Transmission Transmission and isochronous.
·         Synchronous Transmission
Synchronous Transmission is a form of transmission that transmits serial data or information continuously. Transmission of this type often face the problem, namely the problem of synchronization and bit synchronization character.
The main problem in synchronizing bit is matter of time when the transmitter started putting bits to be transmitted to the transmission medium and when the receiver must know the right time to take the bits that are sent them.
            This problem can be solved with existing clock and clock ditransmitter there direceiver. Clock on the transmitter will tell when to put the bits to be transmitted, for example if you want to send with a capacity of 100 bps, the clock on the transmitter is set to work with a clock speed of 100 bps and the receiver must also be set to pick up from the transmission lines 100 times each second.

            The second problem is the character in Synchronous Transmission synchronization. The problem is in the form of determining a number of bits which are a bits forming a character. This can be overcome by giving SYN character. Generally two or more SYN transmission control is placed in front of the block of data transmitted.
If only used a character kintrol transmission errors can occur false synchronization. To prevent false synchronization, two SYN control characters can be used at the beginning of the block of data being transmitted. Receiver after identifying the form of the first SYN, and then identify the next 8 bits, if it is a SYN control the second character, then after that it starts to count every 8 bits and assemble into a character.

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