Branch circuit re-timing system

Abstract

This invention relates to a re-timing system for branch channels including a phase locking loop, a time pick up device, a buffer storage, a frequency tester and a reading clock selector, in which, said time pick up device is used in processing the input signals of branch E1 and picking up write-clock signals from it to write data in E1 signals into said buffer-storage by the write-clock, said phase-lock loop is used in locking an outside primary source, the output-clock of which is provided to the read-clock to be selected, said frequency tester is used in testing the relative frequencies andrelative frequency deviations of the write-clock and read-clock of the storage, the input of said read-clock selector is the output clock of the phase-locking clock and the write clock of the time pick-up device and the selector selects an input in which as its output and its output clock is taken as the read clock of the buffer-storage.

Description

technical field [0001] The present invention relates to a synchronous digital hierarchy (Synchronous Digital Hierarchy, SDH), in particular to a branch retiming system. Background technique [0002] At the end of the SDH transmission network, due to geographical location, transmission equipment, etc., the E1 signal output by the SDH branch has a lot of phase noise; and the service equipment has no other suitable channels to obtain clock synchronization information, which eventually leads to communication failures. The abnormality is mainly manifested in the following two aspects. [0003] One: The main way for service equipment to obtain timing reference is to extract synchronous clock from 2Mbit / s circuit with service, and there must be phase noise such as large or small drift in the timing reference, and the service equipment will be sensitive to the input phase The noise is amplified and then output. At the same time, the service equipment will also generate additional f...

AI Technical Summary

Problems solved by technology

[0003]One: The main way for business equipment to obtain timing reference is to extract synchronous clock from 2Mbit / s circuit with service, and timing reference must have large or small The drift and other phase noise, and the business equipment will amplify the input phase noise and then output it. At the same time, the business equipment will also generate additional drift phase noise superimposed on the output. Therefore, the timing reference is passed through several stages in a timing chain After that, the quality will inevitably degrade

[0004] Two: One of the shortcomings of the SDH transmission network is that the PDH (Plesiochronous Digital Hierarchy, quasi-synchronous digital system) branch output signal of SDH cannot be used as a timing reference

[0007]However, since there may be a large frequency deviation between the clock extracted by the timing extraction device from the branch E1 signal and the reference clock of the retiming system, the buffer memory Missing or re-reading occurs, which affects the normal reception of data from business equipment, which in turn affects the normal operation of business equipment

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