Data Transmission

simplex data transmission is when the data is transmitted in only one direction.

For example: data being transfer from a computer to a printer.

Half-duplex data transmission is in both directions but not at the same time.

For example: A phone conversation between two people where only one person speaks at a time.

Full-Duplex data transmission is on both sides simultaneously.

For example: broadband connection on a phone line.

serial data transmission is when data is sent, one bit a time, over a single wire or channel. Bits are sent one after another in a single stream. This method of data transmission works well over long distances. However, data is transmitted at slower rate. Since only one wire or channel is used , there is no problem of data arriving its destination out of synchronization.

Parallel data transmission is when several bits of data, usually one byte, are sent down in several wires or channels at the same time; one wire or channel is used to transmit each bit. this method of data works well over short distances, over longer distances the data bits can become skewed - this means they will no longer be synchronized.

Asynchronous data transmission refers to data being transmitted in an agreed bit pattern. data bits, 1s and 0s, are grouped together and sent with control bits. control bits are the bits which are attached before and after the byte which is being transmitted. this means that the receiver of the data knows when the data starts when it ends. this prevent data being mixed up; without these control bits, it would impossible to separate these groups of data as they arrived.

Synchronous data transmission is a continuous stream of data. the data is accompanied by timing signals generated by an internal clock. this ensures that the sender and receiver are synchronized with each other. The timing signals must be so accurate here since there are no control bits sent in this type of data transmission. However, is a faster data transfer method then Asynchronous and is therefore used where this is an impotant issue.

FROM CAMRIDGE BOOK COMPUTER SCIENCE