For data transmission various methods are used:-
- Synchronous Transmission
- Asynchronous Transmission
This method of data transmission involves block of characters that are transmitted at regular time sequences. Each of the block of characters is marked with synchronization characters. The receiving end, accepts the data block, till it detects the ending character or after a predefined number of characters are received, indicating end of a message.
This transmission, uses the faster channel and is used when the data transfer requirements exceed several thousand bits/sec. Synchronous transmission is adopted in direct computer to computer communication for larger computer systems because of the requirements for high speed data transfer.
For error detection in data transmission synchronous transmission uses a special method, known as CRC (Cyclic Redundancy Check). This method involves application of an algorithm to the data blocks before they are transmitted. The CRC identifier is used to make out the calculation or computation which is added to the data block. On the receiving end, the same algorithm is used and the result are compared with the CRC received. If they are matching, it implies that the data is transmitted error free else error has occurred.
This method of data transmission involves transmission of data, character by transmission of data, character by character at a time. These characters are transmitted and controlled using start and stop bits.Every character is enclosed between start and stop bits. At the receiving end these characters synchronize to complete the data transferred. This transmission is usually slow,but is less expensive methods of data transmission.