Dynasty digit* or as more.... SD to a friend (SDH) standard for communication high-speed on fiber-optic or radio link. This is the standard that of the standard, more, PHP, HTML (PDH)* originated to some the name of CM* as well. CM SONET, generally, the standard used in the US and Canada is that the direction of data transfer simultaneously, such as DS1,mature DS1 non-simultaneous, such as ATM widely used in telecommunication.

SD name of the standard is that by IP or IO in the standard iPhone or Yu-Ji.707 is designed. Standard CM belongs to Annecy, have been separately designed. Both the standard similarity to each other. Though the SD to a friend, slightly wider than CM is, but more differences in the two standard naming segmenting data returns. This article exclusively to the international standard pays.

in the system SD to a friend, contrary to PHP, HTML to separate one-time contains the original data* a higher level (e.g., E1) does not need to reopen the signal level will not be high, this reduces the access time and ... the complexity and fuzzies that the price of equipment will be.

in SD a friend signal integration* The *, etc. for the flow of optical fiber, or radio signal link, the relay radio or satellite links, or for electrical cable, coaxial, intercom, and transferred.

SD to a friend in 1992, the telecommunication network was introduced, and since then, with growth rapid in all levels of the structure of the network communications is handled. Including network access, urban, long-distance. This system, as it was based on the old system, PHP, HTML, and improve it, especially in terms of discussing the timing * was created. Unlike PHP, HTML, signals SD to a friend are standard complex system for the extraction and the same time, Clock different. The rules and standards of the SD to a friend by CC IP t-t (ITU or CCITT) has been developed.