Data transmission
Data transmission (data てんそう) is to transfer some kind of data and information from a certain place to another place. An express messenger is employed and was performed by a relay of an open-air fire and the roof truss communication once, but is it copper afterwards? It came to be performed using a Morse code on a line.
Furthermore, I made full use of various techniques and, using telex and a computer, came to transmit the stream of a bit or the byte. Transfer means includes copper wire, optical fiber, a laser, radio, infrared rays. For example, data transmission is carried out for a Web browser from a Web server by accessing the Web site, and taking data out of a storage device. But movement of data and the information to the distant place and technique to send off include transfer and transmission, and these are distinguished.
A concept about the data transmission includes communication protocol. There is much communication by the packet-based protocol now.
Kind
- Serial (series) transfer
- I send data as bit string in one line. I spend only 1 bit in once, but the transfer rate can speed up. Generally, I am used for long-distance transfer by giving check digit and parity bit.
- Parallel (parallel) transfer
- Using several lines, I can transfer plural bits in parallel at the same time. I can raise the data transfer rate than serial transfer. I am often used in the computer inside and am used by the connection with the internal bus and printer. The characteristics of individual lines are delicately different to use the plural lines, and the problem is the point that unevenness is easy to produce at the time when a bit arrives at the other party. If this becomes bad, message contents are broken and lose a meaning. Therefore, the parallel transfer is not suitable for a long distance.
Synchronization data transmission and async data transmission
By the async data transmission, I add start bit and stop bit before and after bit string to express letters such as ASCII and transfer it at 10 bits. For example, it becomes "1 0100 0001 0" when I transfer "0100 0001". Though the reception side detects initiation and termination of the transfer of the letter, these are used. When data are transferred intermittently, this method is used and is not used when I am transferred continually. Generally, start bit and the stop bit are placed to become the reverse polarity. The reception side can in this way detect the next packet was transmitted.
By the synchronization data transmission, start bit and the stop bit are not used and synchronize a transfer speed using a clock signal on the transmission side and the reception side. And I transfer data continually. A data transfer rate rises as much as there are not start bit and stop bit, but an error becomes easy to occur when clock synchronization collapses. In addition, there is the period when they cannot transmit and receive the reception side in a protocol, and the transfer data of the meantime are lost. I establish the resynchronization system of the clock to deal with such a problem and allow you to confirm it whether you were received using check digit definitely by a byte credit.
Allied item
This article is taken from the Japanese Wikipedia Data transmission
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