JPH02306740A - Subsequent synchronizing system - Google Patents

Abstract

PURPOSE:To eliminate the need for the installation of a network synchronization device and to confirm a fault of a digital transmission line in the unit of paths by selecting a normal system clock with a digital exchange itself based on fault information in the unit of digital transmission lines so as to apply subsequent synchronization. CONSTITUTION:A synchronizing multiplexer 3 changes over a switch 34 when a fault takes place in a transmission line 200 and applies a fault information notice to an exchange 5. The digital exchange 5 is provided with a fault monitor section 50, a normal system clock selection section 52, a self-running clock source 54 and a changeover switch 56, and a fault monitor section 50 applies fault discrimination based on the fault inform 302 and sends the result 100 to the clock selection section 52 to select and command a clock supply line 301. The normal system clock selection section 52 based on the fault monitor result 100 selects a normal system clock among synchronization clocks and outputs the selected clock and the synchronizing clock is always supplied in the inside of the exchange 5 by the changeover processing of the switch 56. Thus, the network synchronizing device is not required and fault detection is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a slave synchronization system, and more particularly to a slave clock synchronization system in a digital exchange.

(Prior Art) As is well known, in digital communication and the like, in order to extract a signal without error on the receiving side, it is necessary to synchronize the clock frequencies of the transmitting side and the receiving side. An example of such a synchronization method applied to a digital exchange is a slave synchronization method. In this system, the digital exchange operates in synchronization with the synchronized clock from the digital network to which it is connected. Specifically, the digital exchange includes, for example, a synchronous multiplexer fM
It is connected to the transmission path of a digital network via the network synchronizer (UX), and performs synchronous operation by receiving the synchronized clock from this network extracted by the synchronous multiplexer via the network synchronizer TDC3I.

A network synchronization device is a device installed to keep the network synchronization clock normal. That is, the network synchronizer receives synchronization clocks from a plurality of synchronization multiplexers, selects one of the clocks, normal or locked, and supplies it to the digital exchange. When the network synchronizer detects an abnormality in the selected clock due to, for example, a failure in the transmission line, it always maintains the normal clock supplied to the digital exchange by switching to another normal or locked clock. The network synchronizer also has a clock source as a free-running function, and upon recognizing, for example, the occurrence of a total transmission path failure, supplies the synchronization clock of this clock source to the digital exchange.

In addition, if the cable between the network synchronizer that supplies the synchronized clock and the digital exchange becomes abnormal due to a failure such as a cable break, the digital exchange can operate independently by switching to its internal free-running clock source. Do this.

(Problems to be Solved by the Invention) However, such conventional techniques have the disadvantage that a network synchronization device must be installed in order to maintain normal network synchronization, which increases the size of the system. Furthermore, when all the digital transmission lines that receive the network synchronized clock become impaired, the network synchronization device uses its self-running function to switch from the network synchronized clock to the free-running clock and supplies the synchronized clock to the digital exchange. However, with digital exchanges,
Since it is not possible to determine whether the clock is synchronized with the network or the free-running clock of the network synchronizer, there is also the problem that failures in the digital transmission path cannot be recognized.

The present invention eliminates the drawbacks of the prior art, simplifies the system by eliminating the need for a network synchronization device, and provides a dependent synchronization method that enables failure detection of digital transmission paths on the digital exchange side. The purpose is to

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a digital network having a main clock source that generates a network synchronized clock, and a digital network connected to the digital network via a digital transmission line. A synchronous multiplexer that extracts a network synchronized clock from In a dependent synchronization system in a communication system having an exchange, each of a plurality of synchronous multiplexers has a first one that sends a network synchronization clock.
is connected to the digital exchange by a signal line and a second signal line that sends transmission path failure information, and the digital exchange
Based on the fault information sent by the signal line of
A normal system clock is selected from among the network synchronized clocks sent from the signal line, and one selected network synchronized clock is used as the synchronized clock in data communication.

(Function) According to the present invention, the synchronous multiplexing device installed in each of the plurality of digital transmission paths between the digital exchange and the digital network supplies the digital exchange with a synchronous clock extracted from the digital transmission path. .

When the synchronous multiplexer detects an abnormality in the synchronous clock,
Switches the synchronous clock to a free-running clock and outputs a failure notification to the digital exchange. When the digital exchange receives a fault notification, if it has selected the network synchronous clock corresponding to the fault notification, it selects and outputs the network synchronous clock received from the other signal line l.

(Embodiment) Next, an embodiment of the slave synchronization method according to the present invention will be described in detail with reference to the accompanying drawings.6 Referring to FIG. 1, a data communication system showing an embodiment of the slave synchronization method according to the present invention will be described. A relay scheme diagram is shown. The digital network 2 is a communication network composed of, for example, an exchange that exchanges digital signals and a transmission network that transmits digital signals, and has a main clock that is a network synchronization clock source. It has l. For example, the digital network 2 is 1.51
It is connected to synchronous multiplexers 3-0 to 3-n via digital transmission lines 200-0 to 200-n that transmit digital signals at a transmission rate of Jbit/s.

The synchronous multiplexer 3 is a multimedia synchronous multiplexer for, for example, a high-speed digital line, and is equipped with a failure detection function in the digital transmission line 200, and is a multiplexer for efficiently transmitting media such as voice, data, images, or images. It is a device that converts The multiplexers 3-0 to 3-n are connected to the digital exchange 5 via digital transmission lines 300-0 to 300-n, respectively, and convert data to a transmission rate according to the transmission medium to transmit data with the exchange 5. Let's do it.

The synchronous multiplexing device 3 includes a synchronous clock extraction section 30, a free-running clock source 32, and a changeover switch 34. The clock extractor 30 is a circuit whose input side is connected to the digital transmission line 20 and extracts the network synchronized clock 1 of the main clock source 1 from the information sent from this. The output side of the extractor 30 is connected to one input terminal of the switch 34, and outputs the extracted network synchronization clock l thereto.

The other input terminal of the switch 34 is connected to the free-running clock source 32, and the output terminal thereof is connected to the clock supply line 301.
It is connected to the digital exchange 5 via. switch 3
Reference numeral 4 denotes a changeover switch that sends the clock of either the tarlock extractor 30 or the free-running clock source 32 to the exchange 5 as a synchronous clock. That is, the switch 34 is normally connected to the clock extraction section 30 side and sends the extracted network synchronized clock 1 to the digital exchange 5. Further, when a failure is detected in the digital transmission line 200 to which the device 3 is connected, the switch 34 is switched to the clock source 32 side under the control of the control unit (not shown) of the device 3, and the network synchronized clock l Instead, the free-running clock 32 is sent to the exchange 5.

The synchronous multiplexer 3 is also connected to the digital exchange 5 via a fault information line 302. When a failure occurs in the transmission path 200, the multiplexing device 3 switches the switch 34 and connects the exchange 5 through the information line 302.
Failure information will be notified.

The digital exchange 5 has signal lines +300-D to 300-n.
.

301-0 to 301-n, 302-0 to 302-n) to synchronous multiplexers 3-0 to 3-n.

Switchboard 5 is.

It has a fault monitoring section 50, a normal system clock selection section 52, a free-running clock source 54i5, and a changeover switch 56.

The fault monitoring unit 50 monitors each fault information line 302-0 to 302- of the synchronous multiplexer 3 connected to the exchange 5.
connected to n. The monitoring unit 50 collects this information, II
The monitoring unit 50 also determines a failure based on the failure notification 302 sent from the clock supply line 302 and sends the failure monitoring result 100 to the clock selection unit 52 to instruct selection of the clock supply line 301. line 301-0
~301-n are also connected. The monitoring unit 50 also detects a transmission path failure in the clock supply line 301 by monitoring the synchronous clock from the supply line 301. That is, even if the monitoring unit 50 does not receive a fault notification through the monitoring information line 302, if an abnormality is found in the corresponding clock supply II 301, the monitoring unit 50 sends the monitoring result 100 of fault determination to the selection unit 52.

The normal system clock selection unit 52 connects the clock supply line 301-
This is a selection circuit that is connected to the Fs fault monitoring results 100 and selects a normal clock from among the synchronized clocks sent from the Fs damage monitoring result 100 and outputs it.

The clock selection unit 52 selects the selected normal system clock 102.
is output to one input terminal of the selector switch 56.

The switch 56 has the other input terminal connected to the free-running clock source 54.
It is connected to the. The switch 56 is a changeover switch that sends the synchronous clock input from any of these input terminals to the inside of the exchange 5. That is, the switch 56 is
Normally, it is connected to the clock supply line 301 side, and when the fault monitoring unit 50 determines that all network synchronized clocks l have become abnormal, its contact is switched to the clock source 54 side. Through this switching process, a synchronous clock is always supplied to the interior of the exchange 5.

For example, through clock supply line 3 old-〇, switch 5
Assume that the clock selection unit 52 selects the network synchronization clock l from the multiplexer 3-0, which is supplied to the multiplexer 3-0. At this time, if the multiplexer 3-0 detects a fault in the digital transmission path 200-0, the multiplexer 3-0
4-O from the clock extractor 30-0 to the free-running clock 32
-0, and sends a failure notification to the failure monitoring unit 5o of the exchange 5 via the failure information line 302-0.

When the fault monitoring unit 50 receives a fault notification from the multiplexing device 3-0, the fault monitoring unit 50 transmits the normal system clock selection unit 52 via the control line 100.
Instructs to switch the network synchronized clock 1. Selection section 5
2 receives this instruction, clock supply line 301-0
A normal network synchronization clock l is supplied from the network. For example, switching to supply line 301-1 always synchronizes the system dependent on the network's main clock source l.

Further, when the fault monitoring unit 50 detects that all of the plurality of digital transmission lines 200-0 to 200-n have failed, the clock selection unit 52
The system is operated by selecting one of the 3-n free-running clock sources 32-O to 32-n and synchronizing the exchange 5 with it.

Further, even if any of the clock supply lines 301-0 to 301-port becomes abnormal due to a failure such as a cable breakage, the failure monitoring unit 50 detects this abnormality. 52 has selected the clock 32 from the clock supply line 301 in which an abnormality has been detected, the failure monitoring unit 50 instructs the clock selection unit 52 to switch to another normal clock 32. Also,
The failure monitoring unit 52 connects the clock supply lines 3010 to 301-n
If it is detected that all of the clocks are abnormal, the digital exchange 5 switches to the self-running clock source 54 using the switch 56, and operates the exchange 5 itself independently.

FIG. 2 shows a relay scheme diagram according to another embodiment of the dependent synchronization scheme according to the present invention. In this figure, elements similar to those shown in FIG. 1 are designated by the same reference numerals. This embodiment differs from the previous embodiment in that the synchronous multiplexer 4 is not provided with a free-running clock 32.

That is, in the case of the same embodiment, when the synchronous multiplexer 4 detects a fault in the 20 digital transmission lines, the fault notification line 30
2, the failure is notified to the failure monitoring unit 50. Monitoring section 5
Upon receiving this notification 302, the primary failure monitoring unit 50 switches the switch 56 to the free-running clock 54 side.
The clock selector 52 is controlled via the control line 100 to select the synchronous multiplexer 4 that is outputting a normal network synchronized clock l. After the selection section 52 selects the normal network synchronized clock 1, the switch 56 is switched to the clock selection section 52 side, and the network synchronized clock I is sent to the inside of the exchange 5. If all the network synchronized clocks 1 fail, the exchange 5 itself is operated independently using the clock 54 as in the previous embodiment.

(Effects of the Invention) As described above, according to the present invention, the digital exchange itself selects the normal system clock and performs slave synchronization based on the fault information for each digital transmission path, which is not necessary in the past. It is no longer necessary to install a network synchronization device.

Furthermore, a failure notification route is set between the synchronous multiplexer and the digital exchange for each digital transmission path. Therefore, the digital exchange can detect failures in digital transmission paths on a route-by-route basis. Therefore, digital exchanges, including systems in which a single digital transmission line that does not require a conventional network synchronizer, is connected to a digital exchange via a single synchronous multiplexer, It becomes possible to perform blockage processing for the corresponding channel.

Furthermore, if the digital exchange detects a fault on a different line route from the synchronous multiplexer, it will determine that it is a fault in the digital transmission path, and if it detects an abnormality in the clock supplied from the synchronous multiplexer, it will It can be determined that this is a fault in the digital transmission line and not a fault in the digital transmission line. Therefore, the digital exchange has the advantage that it can block the corresponding channel only when a failure is notified from the synchronous multiplexer to the digital exchange via another line.

[Brief explanation of the drawing]

FIG. 1 is a relay method diagram showing an embodiment of the dependent synchronization method according to the present invention, and FIG. 2 is a relay method diagram showing another embodiment of the dependent synchronization method according to the present invention. Description of main parts 1. Main clock source 2. Digital network 3.4. , synchronous multiplexer 5, , digital exchange 30, clock extractor 32.54, free-running clock source 34,56, , selector switch 50, , failure monitoring unit 52, , normal system clock selection unit 200 ,
, , Digital transmission line patent applicant Oki Electric Industry Co., Ltd. Representative number Takao Maruyama

Claims (1)

[Claims] 1. A digital network having a main clock source that generates a network synchronized clock; and a synchronous multiplexer connected to the digital network via a digital transmission path and extracting the network synchronized clock from the digital transmission path. and a digital exchange that is connected to the digital transmission line via a plurality of the synchronous multiplexers and performs data communication by receiving the network synchronization clock extracted by the synchronous multiplexers. In the dependent synchronization method, each of the plurality of synchronous multiplexers is connected to the digital exchange by a first signal line that transmits the network synchronization clock and a second signal line that transmits failure information of the transmission path, and The digital exchange selects a normal system clock from among the network synchronization clocks sent from the first signal line based on the fault information sent from the second signal line, and A dependent synchronization method characterized by using a clock as a synchronization clock in data communication. 2. In the slave synchronization system according to claim 1, the digital exchange is connected to a plurality of first signal lines, and the digital exchange is connected to a plurality of first signal lines, and the signal is sent by a first signal line selected from the plurality of first signal lines. a clock selection means that outputs the network synchronized clock that has been transmitted; and a clock selection means that is connected to a plurality of second signal lines, and is connected to a plurality of second signal lines, and the clock selection means is connected to a plurality of second signal lines, and the clock selection means outputs the first signal line. 1. A dependent synchronization method comprising: fault monitoring means for issuing selection instructions.