Transmission types

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• Asynchronous transmission
• Plesiochronous transmission
• Synchronous transmission

Asynchronous transmission
Asynchronous transmission is transmission of data in which time intervals between transmitted characters may be of unequal length. Transmission is controlled by start and stop bits at the beginning and end of each character. Transition of signals do not occur at the same nominal rate Generally free running quartz oscillators derive the clock, there is no timing pulses sent from transmitter to receiver

Plesiochronous transmission
Plesiochronous is a Greek word meaning Almost Synchronous, but not fully synchronous. The digital transitions in the signals occur at almost the same rate. There may be a phase difference between the transitions of the two signals, and this would lie on specified limits.

Synchronous transmission

The digital transitions in the signals occur at exactly the same rate. There will be no phase difference between the transitions of the two signals, and this would lie on specified limits. In a synchronous network, all the clocks are traceable to one primary reference clock (PRC). The accuracy of the PRC is better than 0.1 in 1011 and is derived from a cesium atomic standard.

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