plesio-, plesi-

Derived from the Greek plesio, "near", "close", and chronos, "time", and refers to the fact that plesiochronous systems run in a situation when different parts of the system are almost, but not quite perfectly synchronized.

Almost synchronous refers to a transmission where the sending and receiving devices are synchronized, but set to different clocks. Although the bits may not arrive in the same time slot as they were sent, as long as they arrive within a certain, defined range, the transmission is said to be plesiochronous.

The term is used in the "Plesiochronous Digital Hierarchy" (PDH), the widely-used system in which the transmissions from one continent (such as North America) are internetworked with transmissions in other continents (such as Europe) by making small adjustments in the differing data rates between the systems. The European and American versions of the PDH system differ slightly in the details of their functions, but the principles are the same.

A plesiochronous situation can arise when two systems have slightly different clock readings over time. In such circumstances, one of the components, or a third system, would need to notice the mismatch and make some compensating adjustments, such as repeating or deleting a data packet or frame.

A digital correspondence network that is nearly synchronized: Plesiochronous communications describes a communication system where transmitted signals have the same nominal digital rate but are synchronized on different clocks.

The original character of a branching phyletic lineage, found in the ancestral forms.

Similar in form.

1. Similarity in form.
2. Close to or nearly the same shape.

1. Nearly alike in form.
2. Characterized by a form which is similar or like another one.

An ancestral or primitive character.

An evolutionary trait that is homologous within a particular group of organisms but is not unique to members of that group and therefore cannot be used as a diagnostic or defining character for the group.

For example, vertebrae are found in zebras, cheetahs, and orangutans; but the common ancestor in which this trait first evolved is so distant that the trait is shared by many other animals. As a result, possession of vertebrae sheds no light on the phylogenetic relations of these three species.

A symptom exhibited by tissues not yet dead but in the process of dying; wilting for example.

Increased convexity of the crystalline lens, producing myopia; a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than on it; nearsightedness; short sighted.

A “near” (“approximate to the Saurians”) from Early Jurassic Europe (England and Germany). It was not a dinosaur. Named by De la Beche and William Daniel Conybeare in 1821.

Nearly simultaneous; (broadly) happening at the same time: Plesiosynchronous bit sources are not ensured to have precisely the corresponding timing although the nominal bit rate is the very same.

A specimen that has been annotated by someone other than the original author, yet determined to belong within the same classification as the type specimen.