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Asynchronous transmission
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Plesiochronous transmission
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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.