Asynchronous & Synchronous Transmission

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  • 0:04 What Is Transmission?
  • 0:30 Types of Transmission
  • 3:18 Protocols
  • 3:59 Bandwidth
  • 4:30 Lesson Summary
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Lesson Transcript
Instructor: Lyna Griffin

Lyna has tutored undergraduate Information Management Systems and Database Development. She has a Bachelor's degree in Electrical Engineering and a Masters degree in Information Technology.

In this lesson, we'll examine the different types of data transmission techniques in information technology. We'll look at synchronous and asynchronous transmissions and the value bus cycles and bandwidth bring to the transmission process.

What Is Transmission?

Transmission is the action of transferring or moving something from one position or person to another. A letter can be handed to you, received in the mail, read to you, or received by via email. These are all different methods of transmitting the letter. Likewise, in information systems, data transmission is the transferring of data from one system component to another. There are different types and methods of data transmission.

Types of Transmission

Information technology deals with the manipulations and transmission of data and digital signals. Data is usually in the form of bits and bytes. A byte is a unit of data (digital information) consisting of 8 bits.

Synchronous transmission

The word synchronous refers to things happening at the same time. This holds true for synchronous transmission within the context of information technology. Synchronous transmission is, therefore, defined as the process by which data or a signal is transferred from one application system or device to another at constant periods or intervals, usually monitored by a clock. This means that the transmitting and receiving systems send and receive data at the same rate or speed. They are in sync. An example of this is copying data from one file location to another:


In this diagram, data is being transmitted from A to B, A being the sender and B being the receiver. A couple of sync data packets initialize the transmission process. The sync packets, once received by the receiver, are decoded and serve to synchronize the receiving clock with the sending clock. Once synchronization is achieved, sending and receiving commences.

Bus Cycles

Remember that a computer system is made of different components all working together to process information. As such, the computer is characterized by a constant stream of data and signals between its components. Because of this, a bus system of communication is another mode of data transmission used between the corresponding components. City buses serve to take people to different destinations all around town, and a bus can serve multiple locations.

The same concept applies to bus cycles in technology. They can be accessed and used to service different components within the computer system, with clocks used to synchronize flow and keep streams flowing smoothly. A bus cycle is therefore defined as the time it takes to complete a single transaction between one component and another. An example is a single read/write operation. The transmission is done in synchronization with the computer's clock.

Asynchronous Transmission

In the case of asynchronous transmission, the data or signals being transmitted and received are not done in synchronization. The time interval between the sending and receiving devices enable transmission and reception at their own pace. This means the data sending transmitter may not be at the same rate as the data receptor. This mode of transmission is not monitored by the same rate and the transmission is said to be asynchronous. For example, observe the data transfer:


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