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Synchronous Transmission vs. Asynchronous Transmission: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 5, 2023
Synchronous Transmission requires a shared clock signal for data transfer, while Asynchronous Transmission transfers data using start and stop bits without a shared clock.

Key Differences

Synchronous Transmission and Asynchronous Transmission are two primary methods used to transmit data between devices in computing and telecommunications. Synchronous Transmission relies on a shared clock signal between the sender and receiver, ensuring that data is sent and received at fixed intervals. This shared timing allows for efficient and rapid transfer of large amounts of data, making it suitable for applications where constant stream or high speeds are necessary.
In contrast, Asynchronous Transmission does not depend on a shared clock signal. Instead, it uses start and stop bits to signal the beginning and end of a data byte, respectively. The absence of a shared clock means that the transmitting and receiving devices might not always be perfectly synchronized in terms of timing. Therefore, there can be slight and variable delays between data bytes, which are accommodated by the use of the aforementioned start and stop bits.
While Synchronous Transmission can efficiently handle large blocks of data, Asynchronous Transmission is often preferred for scenarios where data is sent sporadically or in smaller quantities. Common everyday examples include computer keyboards and serial ports, where data packets are sent intermittently.
An advantage of Asynchronous Transmission is its simplicity and flexibility, allowing it to adapt to varying intervals between data transmissions. Synchronous Transmission, on the other hand, requires precise coordination between devices, often making it more complex to implement but offering advantages in speed and consistency for large data transfers.
Both Synchronous Transmission and Asynchronous Transmission have their own strengths and are chosen based on the specific needs of a communication system. Factors such as data size, frequency, and the required speed often dictate the choice between them.

Comparison Chart

Timing Mechanism

Shared clock signal
Start and stop bits

Data Transfer Rate

Typically faster
Typically slower

Use Case

Large, continuous data streams
Intermittent, sporadic data transfers


Higher, due to need for synchronization
Lower, due to flexibility in data transmission timing

Example Applications

Digital telephony, video streaming
Computer keyboards, serial ports

Synchronous Transmission and Asynchronous Transmission Definitions

Synchronous Transmission

Data transmission where sender and receiver share a clock signal.
In digital telephony, Synchronous Transmission ensures clarity and speed.

Asynchronous Transmission

Simpler to implement than synchronous methods.
Due to its simplicity, Asynchronous Transmission is common in many consumer devices.

Synchronous Transmission

Offers speed and consistency at the cost of complexity.
For mission-critical applications, Synchronous Transmission is often chosen despite its complexity.

Asynchronous Transmission

Suited for intermittent data transfers with variable intervals.
Serial ports often rely on Asynchronous Transmission due to its flexible timing.

Synchronous Transmission

Typically utilized for bulk and regular data transfers.
Satellite communication uses Synchronous Transmission to handle vast amounts of data.

Asynchronous Transmission

Allows for adaptability in data transmission timing.
In environments with unpredictable data flow, Asynchronous Transmission is beneficial.

Synchronous Transmission

A method that sends data in a continuous stream at regular intervals.
For real-time video streaming, Synchronous Transmission is often the preferred method.

Asynchronous Transmission

Data transmission that uses start and stop bits without a shared clock.
Computer keyboards typically use Asynchronous Transmission for keypresses.

Synchronous Transmission

Requires precise timing between transmitting and receiving devices.
High-speed networks employ Synchronous Transmission for data consistency.

Asynchronous Transmission

Typically slower than synchronous methods but offers flexibility.
While not as fast, Asynchronous Transmission is often chosen for its adaptability.


In which scenario would Asynchronous Transmission be preferred?

For intermittent or sporadic data transfers, like computer keyboards.

Does Synchronous Transmission always require external clocking?

It requires a shared clock signal, which can be external or derived from the transmitted signal.

Which transmission method is faster?

Typically, Synchronous Transmission is faster for large, continuous data streams.

Which transmission type is more resource-intensive?

Synchronous Transmission can be more resource-intensive due to its need for precise synchronization.

Does Asynchronous Transmission always mean slower data rates?

Not necessarily, but it's typically used for scenarios where high speed isn't the primary concern.

Why does Asynchronous Transmission use start and stop bits?

To signal the beginning and end of a data byte without needing a shared clock.

Can I convert Synchronous Transmission to Asynchronous Transmission?

Conversion is possible through specific interfaces or protocols, but it depends on the application.

Is Synchronous Transmission better for real-time applications?

Often, yes, due to its consistent and fast data transfer rates.

Why is there a need for two different transmission methods?

Different applications have different needs in terms of data size, frequency, and required speed.

What's a drawback of using Synchronous Transmission?

Its complexity and the need for precise coordination between devices.

Can Asynchronous Transmission handle bulk data transfers?

While possible, it's often less efficient than Synchronous Transmission for large data chunks.

Is there a cost difference in implementing the two methods?

The cost varies based on application and required hardware, but Synchronous Transmission might be costlier due to additional synchronization components.

What's a common use case for Synchronous Transmission?

Digital telephony and video streaming often use Synchronous Transmission.

Which is more error-prone: Synchronous Transmission or Asynchronous Transmission?

Both have error-checking mechanisms, but Asynchronous Transmission might have more overhead due to its start/stop bits.

Are there hybrid transmission methods combining both?

Yes, some protocols or systems might employ characteristics of both for specific needs.

How does Synchronous Transmission handle errors?

Often through error-checking protocols and retransmission of data.

Can both methods coexist in a single communication system?

Yes, some systems might use both, choosing based on specific transmission needs.

Is Asynchronous Transmission more complex to implement?

No, it's often simpler than Synchronous Transmission due to its flexibility in timing.

What's the main difference between Synchronous Transmission and Asynchronous Transmission?

Synchronous Transmission uses a shared clock, while Asynchronous Transmission uses start and stop bits.

What's the role of a baud rate in Asynchronous Transmission?

Baud rate defines how many symbols (or bits) are transmitted per second.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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