Plesiochronous system

Plesiochronously comes from the Greek plesio (almost adjacent ) and chronos (time) and is a term of telecommunications.

Two systems work plesiochronously if they use the same nominal clock rate, but smaller deviations are possible. These lead to phase errors, but allow the use of synchronous techniques for some time, during which the phase errors have no effect. After a re- synchronization must occur.

The term is rarely used, but is by the Plesiochronous Digital Hierarchy become topical again. The well-known asynchronous data transfer is asynchronous at the character level, but plesiochronously at the bit level.