JPH04188917A - Automatic line switching device - Google Patents

Abstract

PURPOSE:To normally execute backup even when a fault occurs at a MODEM by detaching the MODEM itself from a communication path at the time of generating the fault. CONSTITUTION:When the fault occurs at a MODEM 12, a carrier detecting signal 14 is turned off, switch part 13 is switched over, a terminal 11 is cut off from the MODEM 12, and connected through a terminal adaptor 21 to an ISDN line 22. Moreover, a monitor control part 23 operates a prescribed calling control to the ISDN line 22 by transmitting a control signal 24 to the terminal adaptor 21, and operates the control for switching a terminal at an opposite station side from the MODEM side to the terminal adaptor side. Then, a data communication is operated through the ISDN line 22 according to a prescribed protocol. Thus, it is possible to easily facilitate a counter measure to the fault of the MODEM 12.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a communication line switching device that detects a failure and automatically switches a communication line to a backup side. The present invention relates to an automatic line switching device that automatically switches lines between networks.

[Conventional technology]

Generally, in communication systems, a backup line is prepared separately from the original dedicated line in case a failure occurs, in order to ensure the reliability of the system.

As this backup line, an analog telephone exchange line is usually used, and a data channel reception carrier detection signal (hereinafter simply referred to as a carrier detection signal) between a modem (hereinafter referred to as a modem) and a terminal is often used. It is designed to monitor and automatically switch lines. This carrier detection signal is a signal indicating whether or not the line signal of the data receiving channel is within a specified range, and is turned on if the received signal is within the specified range, and turned off when it is outside the specified range.

FIG. 2 shows a conventional automatic line switching device. In this figure, one end of the modem 11 is directly interfaced to the terminal 11, and the other end is connected to the switch section 13. Among the interface signals between the modem 11 and the terminal 12, the carrier detection signal 14 is also input to the monitoring control section 15 and is constantly monitored.

The switch unit 13 is connected to a dedicated line 16 and also to a telephone exchange line 18 via a network control unit 17. The switch section 13 and the network control section 17 include a control 8
A control signal 19 is input from 15.

The operation of the conventional automatic line switching device configured as described above will be explained.

In normal times, that is, when the dedicated line 16 is normal, the modem 12 is connected to the dedicated line 16 by the switch section 13. Data from the opposite station is input from the dedicated line 16 to the modem 12 via the switch section 13. The modem 12 performs processing such as predetermined demodulation on the input data, and then sends the input data to the terminal 11. On the other hand, terminal 1
The data sent from the terminal 1 undergoes processing such as predetermined modulation in the modem 12, and then is sent out onto the dedicated line 16 via the switch 13.

On the other hand, if a failure occurs in the dedicated line 16, the carrier detection signal 14 from the modem 12 to the terminal 11 is turned off. The control section 15 detects this and sends a control signal 19 to the switch section 13. As a result, switching is performed and the modem 12 is connected to the telephone exchange line 18 via the network control section 17, and data communication will be performed via the telephone exchange line 18 from now on.

[Problem to be solved by the invention]

In this way, conventional automatic line switching equipment can automatically switch to the backup line side by detecting the off state of the carrier detection signal among the interface signals between the modem and the terminal, but it has the following problems. was there.

In other words, there are two cases in which this carrier detection signal turns off: when a failure occurs in the dedicated line and when the modem itself fails, but in the former case, the line is switched to the backup line side. Even if the dedicated line is later restored and the carrier detection signal is turned on, this cannot be detected, so automatic recovery of the line is not performed. For this reason,
There was a drawback that the operator had to judge and manually switch back from the backup line to the dedicated line.

Moreover, in the latter case, even if the line is switched to the backup line side, data communication cannot be performed because the failed modem itself is present on the route.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an automatic line switching device that can cope with failure of the modem itself and automatic switching back from the backup line to the original line.

[Means to solve the problem]

In the invention as claimed in claim 1, (1) a modem that modulates and demodulates data transmitted and received with a directly connected private line;
(ij) A terminal adapter that performs predetermined call processing between the backup line and (■) An interface signal that indicates whether the received signal is within the specified range between the modem and the data terminal. and (iv) when the carrier detection signal monitoring means detects an off state of the carrier detection signal, the data terminal is switched from the modem to the terminal adapter for connection. The automatic line switching device is provided with connection switching means for switching the connection of the data terminal from the terminal adapter to the modem when the on state of the carrier detection signal is detected.

In the invention as claimed in claim 1, the modem is used as a dedicated line! The terminal is switched between the dedicated line on the modem side and the backup line on the terminal adapter side by connecting the modem and monitoring the carrier detection signal of this modem.

In the invention as set forth in claim 2, the automatic line switching device as set forth in claim 1 is constructed using an integrated service digital network as a backup line.

In the second aspect of the invention, when a failure occurs, data communication is performed using the integrated service digital network.

〔Example〕

The present invention will be described in detail below with reference to Examples.

FIG. 1 shows an automatic line switching device in one embodiment of the present invention. Here, the same parts as in the conventional example (FIG. 2) are given the same reference numerals.

In this figure, the switch section 13 is interface-connected to a dedicated line 16 via a modem 12, and is also interface-connected to an integrated service digital network (hereinafter referred to as an 15DN line) 22 via a terminal adapter 21. There is. The other side of this switch section 13 is connected to the terminal 11 via an interface.

A monitoring control unit 23 is connected to the modem 12 and terminal adapter 21 to perform various controls.

That is, the carrier detection signal 14 of the interface signals between the modem 12 and the switch 13 is transmitted to the supervisory control unit 2.
3, and is constantly monitored by the terminal adapter 21.
Call control is performed using control signals 24. Further, a line switching signal 25 is input from the supervisory control section 23 to the switch 613.

The operation of the automatic line switching device configured as above will be explained.

In normal times, that is, when the modem 12, dedicated line 1116, etc. are normal, the terminal 11 switches the modem 1 to
Connected to the 2nd side. Data arriving from the opposite station via the dedicated line 16 is sent to the terminal 11 via the switch section 13 after being subjected to processing such as predetermined demodulation at the modem 12. Conversely, data sent from the terminal 11 is sent via the switch 13 to the modem 12, where it undergoes processing such as predetermined modulation, and then is sent onto the dedicated line 16.

On the other hand, when a failure occurs in the dedicated line 16, the carrier detection signal 14 is turned off. The supervisory control unit 23 detects this and sends a line switching signal 25 to the switch unit 13. As a result, the switch section 13 is switched, the terminal 11 is disconnected from the modem 12, and is connected to the 15DN line 18 via the terminal adapter 21.

Furthermore, the supervisory control unit 23 sends a control signal 24 to the terminal adapter 21 to perform predetermined calling control for the 15DN line 22, and also controls to switch the terminal on the opposite station side from the modem side to the terminal adapter side. I do. Then, following the prescribed protocol:
Data communication will be performed via the 5DN line 22.

Note that even if the modem 12 itself fails, the line is switched to the 15DN line 22 by the same operation.

Now, when the fault in the dedicated line 16 or the modem 12 is restored, the carrier detection signal 14 is turned on again. The supervisory control unit 23 detects this and sends a line switching signal 25 to the switch unit 13. As a result, the switch unit 13 is switched, and the terminal 11 is disconnected from the terminal adapter 21 and connected to the dedicated line 16 via the modem 12.

Furthermore, the supervisory control unit 23 sends a control signal 24 to the terminal adapter 21 to perform predetermined control to disconnect the line, and also performs control to switch the terminal on the opposite station side from the terminal adapter side to the modem side. . Thereafter, data communication will be performed via the dedicated line 16 according to a predetermined protocol.

〔Effect of the invention〕

As explained above, according to the present invention, by directly connecting a modem to a dedicated line and monitoring the carrier detection signal of this modem, a terminal can be connected between the dedicated line on the modem side and the backup line on the terminal adapter side. Since it was decided to switch between the two, the modem itself would be removed from the communication path in the event of a failure. Therefore, unlike the conventional method, even if a failure occurs in the modem, backup can be performed normally.

In addition, in the present invention, the carrier detection signal continues to be monitored even after switching the line to the backup line, so if the dedicated line is restored and the carrier detection signal is turned on after switching to the backup line, the carrier detection signal is turned on again. Switching to a dedicated line is performed. Therefore, it is possible to automatically switch back to the dedicated line, which has the effect of eliminating the need for conventional manual operations.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an automatic line switching device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional automatic line switching device. 11... terminal, 12... modem, 13
......Switch section, 14...Carrier detection signal, 16...Dedicated line, 22...15DN
Line, 23... Monitoring control unit, 25...
・Line switching signal. Applicant NEC Corporation Agent Patent Attorney Umeo Yamauchi Figure 1: Arm 12 Figure 2: 3

Claims (1)

[Claims] 1. A modem that modulates and demodulates data transmitted and received between a directly connected private line, a terminal adapter that performs predetermined call processing between the backup line, and the modem. carrier detection signal monitoring means for monitoring a carrier detection signal as an interface signal indicating whether or not a received signal is within a specified range; switching and connecting a data terminal from the modem to the terminal adapter when an off state of the terminal adapter is detected;
An automatic line switching device comprising connection switching means for switching and connecting a data terminal from the terminal adapter to the modem when an on state of a carrier detection signal is detected. 2. The automatic line switching device according to claim 1, wherein an integrated service digital network is used as the backup line.