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Data transmission is a way of transmitting digital or analog data over a communication medium to one or more devices. It allows the transmission and communication of devices in different environments: point-to-point, point-to-multipoint or multipoint-to-multipoint.
Data transmission can either be analog or digital but is mostly earmarked for sending and receiving digital data. Thus, data transmission is also referred to as digital transmission or digital communications.
It works when a device aims to transmit a data object or file to one or multiple recipient devices. The digital data comes from the source device in the form of digital bit streams. These data streams are positioned over a communication medium for transmission to the destination device. An outward signal can either be baseband or passband.
Aside from external communication, data transmission may be done internally to a device. The sending of data to a processor from the random access memory (RAM) or hard disk is a form of data transmission.
Types of Data Transmission
- Parallel transmission – Several bits are transmitted together simultaneously with one clock pulse rate. It transmits quickly as it utilises several input and output lines for sending the data.
It uses a 25-pin port with 17 signal lines and 8 ground lines. The 17 signal lines are divided as
- 4 lines – initiates handshaking
- 5 lines – communicates and notifies errors
- 8 lines – transfers data
- Serial Transmission – Data is sent bit by bit from one computer to another in two directions. Each bit has a clock pulse rate. Eight bits are transmitted at a time with a start and stop bit known as a parity bit, which is 0 and 1 respectively. Data cables are used when transmitting data to a longer distance. The data cable has D-shaped 9 pin cable that connects the data in series.
Comparison between Serial and Parallel Transmission
|Basis for Comparison||Serial Transmission||Parallel Transmission|
|Definition||Data flows in 2 directions, bit by bit||Data flows in multiple directions, 8 bits (1 byte) at a time|
|Number of bits transferred per clock pulse||1 bit||8 bits or 1 byte|
|Applications||Used for long distance communication||Used for short distance communication|
|Example||Computer to computer||Computer to printer|
Types of Serial Transmission
There are two types of serial transmission – synchronous and asynchronous both these transmissions use bit synchronization.
Bit synchronization is necessary to identify the beginning and end of the data transmission.
Bit synchronization supports the receiving computer to recognize when data begins and ends during a transmission. Therefore, bit synchronization offers timing control.
Asynchronous Transmission –
- In asynchronous transmission data moves in a half-paired approach, 1 byte or 1 character at a time. It sends the data in a constant current of bytes. The size of a character transmitted is 8 bits where a parity bit is added each at the beginning and at the end which makes it a total of 10 bits. It doesn’t need a clock for integration; rather it utilizes the parity bits to inform the receiver how to translate the data.
It is straightforward, quick, cost-effective and doesn’t need a 2-way communication.
Synchronous Transmission –
- In synchronous transmission, data moves in a complete paired approach in the form of chunks or frames. Synchronization between the source and target is required so that the source knows where the new byte begins since there is no space between the data.
It offers real-time communication between linked devices.
Synchronous and Asynchronous Transmission
|Point of Comparison||Synchronous Transmission||Asynchronous Transmission|
|Definition||Transmits data in the form of chunks or frames||Transmits 1 byte or character at a time|
|Speed of Transmission||Quick||Slow|
|With gap between the data?||Yes||None|
|Examples||Chat Rooms, Telephonic Conversations, Video Conferencing||Email, Forums, Letters|