Plesiochronous
Plesiochronously comes from the Greek of plesio (nearly 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 a certain time, during which the phase errors have no effect. A new synchronization must then take place.
The term is rarely used, but has become topical again due to the plesiochronous digital hierarchy . The well-known asynchronous data transfer is asynchronous on the character level, but plesiochronous on the bit level.