plesiochronous

Plesio means as much as "close to" or "approximately the same". Plesiochronous refers to the temporal relationship between digital signals in which the transmission rates of the signals nominally match, but their real rates differ within specified tolerances. In plesiochronous transmission, the bit rates of the signals may differ from the standardized nominal values.

Plesiochronous Digital Hierarchy( PDH) is an example of a network architecture that uses plesiochronous transmission. Plesiochronous transmission is also used in optical networks.