Special small ISON exchange selecting synchronous pulse source automatically

Abstract

A special minitype exchanger of integrated service data net to automatically select synchronous clock pulse source includes junction chip to be connected with network terminal via junction interface and to be connected with central office via network interface in order to receive output signal of frame synchronous clock and data clock, chip at the client end to be connected with terminal equipoment via interface of the client end to receive pulse output signal of frame synchronous clock and data block, precedence selection circuit to be connected to junction chip, and they to be connected to each other in mode of daisy ring circuit in order to send out pulse output signal of frame synchronous clock and data clock.

Description

technical field [0001] The present invention relates to an integrated services digital network private branch exchange (ISDN PBX for short) and a method for selecting a synchronous clock pulse source and a control method for a digital phase-locked loop, and particularly relates to A dedicated small-scale exchange for integrated service digital network and its method for automatically selecting a synchronous clock pulse source, and a control method for a digital phase-locked loop. Background technique [0002] Known ISDN dedicated small switches such as figure 1 As shown, the ISDN PBX 12 includes N (N is a positive integer) trunk (LT-T) chips 16 and L client (LT-S) chips 18 . The N LT-T chips 16 are connected to a network terminal (network terminal 1, NT1) via a trunk (T) interface, and then connected to a central office (CO) via NT1. And L LT-S chips 18 are connected to terminal equipment (terminal equipment, TE for short) through a subscriber (subscribe, S for short) inte...

AI Technical Summary

Problems solved by technology

[0005] 1. Because it is controlled by software, real-time control cannot be done, so it is difficult to ensure the system performance of ISDNPBX

[0006] 2. Since all outside lines may be connected or hung up at any time, in order to obtain a clock pulse of the outside line being called or connected as a reference, the software needs to be busy with polling (polling) and comparison, thus reducing the system performance

[0007] 3. Increase the complexity of the software program

[0009] 5. Unable to automatically select an appropriate clock pulse source synchronized with the central office

[0010] 6. Since this ISDN PBX cannot automatically select the synchronous clock pulse source, the external DPLL must be in the power-on state, which increases power consumption

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