JPH02279034A - Line switching device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a data error due to the synchronizing step-out and to surely switch a transmission line to a main high speed digital line by providing a line control means switching an operating line into a main digital line in matching with frame synchronization when the restoration of the main digital line is detected. CONSTITUTION:When a high speed digital line 11 is restored and a transmission line for a digital data is switched from an ISDN network 12 to the high speed digital line 11, frame synchronization is taken to send the head of the digital data through the high speed digital line 11 and the line is switched from the ISDN network 12 into the high speed digital line 11. Thus, the occurrence of a data error due to the synchronizing step-out at switching is prevented completely and the line is switched surely and smoothly to the high speed digital line 11 at al times.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a line switching device for mutually switching between a main digital line normally used for transmitting digital data and a backup ISDN line. .

(Prior Art) As shown in FIG. 4, a conventional line system connecting time division multiplexing devices has a backup digital line 2 in addition to a high-speed digital line 1 that is normally operated, and is used as a data bus. 4 is connected to the high-speed digital line 1 or the standby digital line 2 via the line interface 31 or 32. Incidentally, the ISDN line is used as the backup digital line 2. Therefore, if a failure occurs in the high-speed digital line 1 in operation, the call is connected to the standby digital line 2, and then the data on the data bus 4 is transmitted via the standby digital line 2 via the interface 32. Afterwards, when the failure of the high-speed digital line 1 is restored, the data bus 4 is transferred from the spare digital line 2 to the high-speed digital line! ! 1 side and disconnect the call on the standby digital line 2. But this time, a preliminary digital episode! ! 2 to high-speed digital line 1
When the line is switched to the other side, time-division multiplexed data with a multi-frame structure sent to the high-speed digital line 1 is 1
There was a drawback that frame synchronization could not be achieved unless it started from the beginning of the channel, resulting in an error. Note that when the line is switched from the high-speed digital line 1 to the standby digital line 2, a line error will occur because this is when a failure occurs in the high-speed digital line 1.

(Problems to be Solved by the Invention) As mentioned above, in the line system connecting conventional time division multiplexing devices, a failure occurred in the high-speed digital line that is always in operation, so after switching to the backup digital line, the above When the data transmission path is switched to the high-speed digital line again after the faulty high-speed digital line is restored,
Since the time-division multiplexed data in a multi-frame configuration that is sent to a high-speed digital line is not necessarily from the beginning, there is an inconvenience that synchronization can be lost and data errors can occur. SUMMARY OF THE INVENTION Therefore, the present invention aims to eliminate the above-mentioned drawbacks and, when switching a data transmission line from a backup digital line to a main high-speed digital line, prevents the occurrence of data errors due to loss of synchronization and ensures that the transmission line is switched to the main high-speed digital line. The purpose of this invention is to provide a line switching device that can switch to a high-speed digital line.

[Structure of the invention]

(Means for Solving the Problems) The present invention normally transmits and receives multi-frame digital data using a main digital line, and only during periods when the main digital line is unavailable due to occurrence of a failure, etc., the ISD
In a line switching device that selects either the main digital line or the ISDN network as the line to be used so that the digital data can be sent and received using the N network, recovery detection detects recovery of the main digital line. and the IS
synchronization detection means that detects a predetermined position of digital data transmitted through a DN network and synchronizes the frame of the digital data; and when restoration of the main digital line is detected by the restoration detection means, the synchronization detection means The system is equipped with a line control means for switching the line in use to the main digital line in accordance with the frame synchronization established by the digital line.

(Function) In the line switching device of the present invention, the recovery detection means detects recovery of the main digital line. The synchronization detection means is
A predetermined position of digital data transmitted through an SDN network is detected to synchronize the frame of the digital data. The line control means switches the used line to the main digital line in accordance with the frame synchronization established by the synchronization detection means when the recovery of the main digital line is detected by the recovery detection means.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing an embodiment of a digital communication line system equipped with a digital line switching device of the present invention. .11
is a high-speed digital line that is always in operation, 12 is an ISDN network that is a backup digital line, and 13 is a high-speed digital line 1.
1 and a high-speed digital line interface connecting the data bus 161, and 14 connecting the ISDN network 12 and the data bus 162.
15 is a line switching unit that switches between using the high-speed digital line 11 and the ISDN network 12, and 161 and 162 are data buses.

FIG. 2 is a block diagram showing a detailed example of the line switching device shown in FIG. 1. The line switching unit 15 is connected to the high-speed digital line interface 13 and the ISDNm interface 14 via data buses 161 and 162, and selects either the high-speed digital line 11 or the ISDN network 12 as the line used for transmitting digital data. Select and switch. Further, the high-speed digital line interface 13, the ISDN network interface 14, and the line switching unit 15 are connected to each other by a control bus 17, and lines are switched by control signals transmitted on the control bus 17.

Next, the operation of this embodiment will be explained. Normally, the line switching unit 15 is switched to the high-speed digital line interface 13 side, and digital data is transferred to the data bus 16.
3.161 and the high-speed digital line interface 13 over the high-speed digital line 11.

Here, the digital data has a multi-frame structure of 24 frames as shown in FIG. 3, one frame consists of 24 channels, and each channel has 1 bit of information.

If a failure occurs in the high-speed digital line while the digital data is being transmitted via the high-speed digital line 11 as described above, the high-speed digital line interface 13 detects the failure and transmits the line via the control bus 17. A line switching control signal is output to the switching unit 15. When the line switching control signal is input, the line switching unit 15 activates the SDN network interface 14, connects the call, and switches the line to the ISDN network 12 side.

This allows the digital data to be transferred to the data bus 163 from now on.
．． 162 and ISDN network interface 14.
It is transmitted by the SDN network 12.

After that, when the fault in the high-speed digital line 11 is recovered, the high-speed digital line interface 13 recognizes that the line has been started up due to the recovery from the fault, and first, the high-speed digital line interface 13 connects the opposing high-speed digital line interface 13 via the high-speed digital line 11. communication only to establish normal operation. After that, the high-speed digital line interface 13
The first part of the digital data being transmitted via the DNJM 12 (the first channel shown in FIG.
A line switching control signal is output via the line, frame synchronization is achieved, and the line is switched to the high-speed digital line 11 side. At this time, since the high-speed digital line 11 is a four-wire system with two uplink lines and two downlink lines, the above-mentioned switching of the lines is performed sequentially one uplink line at a time. Switching of the line to this high-speed digital line 11 is performed by the uplink and downlink line switching unit 15.
The operations described above are performed sequentially. In this way, up,
When all the digital data transmitted on each of the two downlink lines has been switched to the high-speed digital line 11 side, the ISD
The NIIQ interface 14 disconnects the call from the ISDN network 12 and enters a standby state with the ISDN network disconnected.

According to this embodiment, the high-speed digital line 11 is restored and
When switching the transmission line for digital days and evenings from ISDN 1112 to high-speed digital line 11, frame synchronization is performed from the beginning of the digital data so that it is transmitted using high-speed digital line 11, and from ISDN network 12 Since it switches to the high-speed digital line 11 side, it is possible to completely prevent the occurrence of data errors due to loss of synchronization at the time of switching, and the high-speed digital line 1 is always connected smoothly and reliably.
You can switch the line to the 1st side.

〔Effect of the invention〕

As described above, according to the digital line switching device of the present invention, when switching a data transmission line from an ISDN network to a main high-speed digital line, data errors due to loss of synchronization are prevented and the transmission line is reliably switched to the main high-speed digital line. You can switch to the digital line side.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a digital communication line system equipped with the digital line switching device of the present invention, and FIG. 2 is a block diagram showing a detailed example of the line switching device shown in FIG. Fig. 3 is a diagram showing an example of the configuration of digital data transmitted by the digital communication line system and line switching device shown in Figs. 1 is a block diagram showing an example of a digital communication line system. 11...High-speed digital line 12...ISDN network 1
3...High-speed digital line interface 14...I
SDN network interface 15...Line switching unit 161.162.163...Data bus agent Patent attorney Hon 1) Takashi

Claims (1)

[Claims] The main digital line is normally used to send and receive multi-frame digital data, and the main digital line is connected to the ISDN network so that the digital data can be sent and received only during periods when the main digital line is unavailable due to failures, etc. In a line switching device that selects either a digital line or an ISDN network as the line to be used, recovery detection means detects recovery of the main digital line; synchronization detection means for detecting and synchronizing the frame of the digital data;
It is characterized by comprising line control means for switching the line in use to the main digital line in accordance with frame synchronization taken by the synchronization detection means when recovery of the main digital line is detected by the recovery detection means. Line switching equipment.