JPH0823391A - Automatic line restoration device - Google Patents

Abstract

PURPOSE:To prevent an opposite modem from being left in an analog public line 1 in the case of line restoration. CONSTITUTION:On the occurrence of a line switching request in a modem 11, a control section 119 commands stop of carrier transmission for a prescribed time to a transmission section 111. Upon the receipt of the command, the transmission section 111 stops the transmission of the carrier. Thus, the reception carrier is interrupted surely in an opposite modem 12. Then the control section 119 commands line switching to line changeover switches 116, 117 when a prescribed time elapses. Thus, a communication line of the modem 11 is switched from an analog public line 14 into an analog private line. This is executed similarly in the cas of occurrence of a line switching request in the modem 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic line restoration device for restoring a communication line connecting two modems from an analog backup line to an analog dedicated line.

[0002]

2. Description of the Related Art Generally, in a communication system in which two modems are connected by a 4-wire analog leased line, when a failure occurs in the leased line, dialing automatically changes the communication line from the analog leased line to the analog line. It is designed to switch to a public line (analog telephone line).

In such a communication system having an automatic line backup function, when the communication quality of the analog public line is deteriorated while the communication of two modems is being backed up by the analog public line, the communication line is changed to the analog public line. Need to switch from analog dedicated line.

In order to realize this line switching, conventionally, one modem first switches a communication line, and the other modem switches the line to switch off the reception carrier or turn off the signal quality detection signal SQD. The communication line was switched by the detection.

Here, the signal quality detection signal SQD is a signal indicating the quality of the received signal. The signal quality detection signal SQD is in an on state (active state) when the quality of the received signal is high, and is in an off state (non-active state) when the quality is low.

[0006]

However, in the above-mentioned configuration, even when the line switching is performed by one modem, the other carrier does not disconnect the received carrier or detects the signal quality. The signal SQD may not be turned off.

This is because, when the line switching is performed by one modem, the terminating resistance of the analog public line to the other modem is removed, so that the carrier transmitted from the other modem is reflected to the receiving section of this modem. Because it goes around.

When such a situation occurs, the line switching trigger is not applied to the other modem, which causes a problem that the modem is left behind on the analog public line.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, a means for stopping carrier transmission for a predetermined time when a line switching request occurs, and a predetermined time after the carrier transmission is stopped. A means for switching the communication line after the elapse is provided.

[0010]

According to the above structure, when a line switching request is generated, carrier transmission stopping means stops carrier transmission. This makes it possible to reliably set the reception carrier of the opposing modem to the disconnected state. After that, when a predetermined time elapses, the line switching means switches the communication line from the analog public line to the analog dedicated line.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, 11 and 12 are modems. Reference numeral 13 is a 4-wire type analog dedicated line for connecting the modems 11 and 12. This analog leased line 13 is the receiving line of the modem 11 and the modem 1.
The line 131 used as the second transmission line and the modem 11
And a line 132 used as a reception line of the modem 12.

Reference numeral 14 has an exchange SW, and when a failure occurs in the analog leased line 13, the analog leased line 1
3 is an analog public line used as a backup line for the third line. The analog public line 14 also includes a line 141 used as a reception line of the modem 11 and a transmission line of the modem 12, and a line 142 used as a transmission line of the modem 11 and a reception line of the modem 12.

In the modem 11, 111 is a transmission unit for modulating a digital signal supplied from a data terminal equipment (DTE) (not shown) and converting it into an analog signal.
A receiving unit 112 demodulates an analog signal sent from the opposite modem 12 and returns it to a digital signal.

Reference numeral 113 denotes a transmission section 111 and a reception section 112.
Is an exclusive line interface for connecting to the analog exclusive line 13. Reference numeral 114 is a public line interface for connecting the transmitting unit 111 and the receiving unit 112 to the analog public line 13. 115 is a DTE for connecting the transmitter 111 and the receiver 112 to the data terminal device.
Interface.

Reference numeral 116 is a line changeover switch for connecting the transmission unit 111 to either the analog dedicated line or the analog public line 14. 117 is the receiving unit 11
2 is a line changeover switch for connecting the analog dedicated line 13 or the analog public line 14.

Reference numeral 118 is an operation unit for a user to perform a line switching operation or the like. A control unit 119 controls the operations of the line selector switches 116 and 117 and the transmission unit 111.

Although not described in detail, the modem 1
2 also has a transmitter 121, a receiver 122, a private line interface 123, a public line interface 124, and a DTE interface 1 having the above-described functions.
25, line changeover switches 126 and 127, an operation unit 128, and a control unit 129.

The operation of the above configuration will be described. First, the line switching operation (line restoring operation) of the automatic line restoring device provided in each of the modems 11 and 12 will be described. In addition,
In the following description, the line switching operation of the automatic line restoration device provided in the modem 11 will be described as a representative.

This switching includes manual switching and automatic switching. Here, the manual switching is switching performed based on an instruction from the user. On the other hand, automatic switching means disconnection of the reception carrier and signal quality detection signal SQD.
Is detected by turning off the switch.

First, the switching operation at the time of manual switching will be described. Now, two modems 11 and 12 are analog public line 1
Backed up in 4.

In this case, the transmission section 111 and the reception section 112 of the modem 11 have the line changeover switches 116 and 1 respectively.
It is connected to the public line interface 114 via 17, and is further connected to the analog public line 14 via this public line interface 114.

In this state, when the user uses the operation unit 118 to instruct switching of the communication line, the operation unit 118 notifies the control unit 119 of this instruction. Control unit 119
Upon receiving this notification, the instructing unit 111 instructs the transmitting unit 111 to stop the carrier transmission for a predetermined time (for example, several seconds). Upon receiving this instruction, the transmission unit 111 stops the carrier transmission for a predetermined time.

After that, the control unit 129 instructs the line selector switches 116 and 117 to switch the communication line when a predetermined time has elapsed. As a result, the transmission section 116 and the reception section 112, in turn, are connected to the leased line interface 113 via the line changeover switches 116 and 117, respectively.
Connected to the private line interface 11
3 is connected to the analog dedicated line 13.

The above is the line switching operation at the time of manual switching. Next, the line switching operation at the time of automatic switching will be described.

The modems 11 and 12 are analog public lines 14
When the reception carrier is disconnected or the signal quality detection signal SQD is turned off in the state of being backed up by, the receiving unit 112 detects this state. When the receiving unit 112 detects this state, it notifies the control unit 119 of this.

Upon receiving this notification, the control unit 119 activates a timer to set the reception carrier cutoff time or SQD.
Measure the off time of. As a result of this measurement, if the disconnection state of the reception carrier or the off state of the SQD continues for a predetermined time, the control unit 119 stops the transmission of the carrier to the transmission unit 111 for a predetermined time (for example, several seconds). Instruct them to do so. Upon receiving this instruction, the transmission unit 111 stops the carrier transmission for a predetermined time.

After that, the control unit 119 instructs the line selector switches 116 and 117 to switch the communication line when a predetermined time has elapsed. As a result, the transmitting unit 111 and the receiving unit 112, in turn, respectively connect the leased line interface 1 to the line changeover switches 116 and 117.
23, and further connected to the analog leased line 13 via the leased line interface 123.

The above is the line switching operation at the time of automatic switching. Although detailed description is omitted, the same operation is executed in the automatic line restoration device provided in the modem 12.

Next, for example, when the user of the modem 11 gives an instruction to switch the communication line, the modem 1
The line switching operation between the automatic line restoration devices provided in Nos. 1 and 12 will be described.

When the user of the modem 11 gives an instruction to switch the communication line, the operation section 18 notifies the control section 119 of that fact. Upon receiving this notification, the control unit 119 instructs the transmission unit 111 to stop the carrier transmission for a predetermined time. Upon receiving this instruction, the transmission unit 111 stops the carrier transmission for a predetermined time.

After that, the control unit 119 instructs the line selector switches 116 and 117 to switch the communication line when a predetermined time has elapsed. As a result, the transmitter 111 and the receiver 112 are connected to the analog dedicated line 13 this time.

On the other hand, when the transmission section 111 stops the transmission of the carrier, the reception carrier is disconnected in the opposite modem 12. As a result, similarly to the modem 11, this modem 12 also executes the process of stopping the carrier transmission and the process of switching the communication line. As a result, in both modems 11 and 12, the communication line is switched from the analog public line 14 to the analog dedicated line 13.

According to this embodiment described in detail above, the following effects can be obtained. (1) First, according to this embodiment, when a line switching request is generated, carrier transmission is stopped for a predetermined time, and the communication line is switched after the stop time elapses. The reception carrier can be reliably set to the disconnected state. This makes it possible to prevent this modem from being left behind on the analog public line without providing special hardware such as a DC inversion detection circuit.

(2) According to this embodiment, the disconnection of the receiving carrier and the turning off of the signal quality detection signal SQD are also included in the line switching request, and when they occur, as in the case where the user gives an instruction, Since the communication line is switched after the carrier transmission is stopped for a predetermined time, the disconnection of the reception carrier or the turning off of the signal quality detection signal SQD does not mean that the transmission of the carrier is stopped by the opposite modem, but that the reception line Even when a failure occurs, it is possible to prevent the opposite modem from being left behind on the analog public line 14.

That is, when a disconnection of the receiving carrier occurs, if the carrier sending operation is not stopped and only the line switching operation is executed, if the disconnection of the receiving carrier is due to the failure of the receiving line, the opposite modem Then, the reception carrier may not be disconnected due to the reflection of the own carrier. As a result, this modem may be left behind on the analog public line 14.

On the other hand, as in this embodiment, even when the reception carrier is disconnected, if the carrier sending operation is stopped, the reception carrier of the opposite modem is disconnected. As a result, even if the disconnection of the receiving carrier of the own modem 12 is due to the failure of the receiving line, the opposing modem is not left behind on the analog public line 11.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment.

(1) For example, in the above embodiment, the case where the present invention is applied to an automatic line restoration device of a communication system using a 4-wire type line as an analog dedicated line has been described. However, the present invention can also be applied to an automatic line restoration device of a communication system that uses a two-wire line as an analog dedicated line.

(2) Further, in the above embodiment, the case where the present invention is applied to an automatic line restoration device of a communication system using an analog public line as an analog backup line has been described. However, the present invention can also be applied to an automatic line restoration device of a communication system using an analog line other than the public line.

(3) In addition to this, it is needless to say that the present invention can be variously modified and implemented without departing from the scope of the invention.

[0041]

As described above in detail, according to the present invention,
When a line switching request occurs, carrier transmission is stopped for a predetermined time, and after this stop time elapses, the communication line is switched, so that the receiving carrier of the opposite modem is surely set to the disconnected state. be able to. This can prevent the modem from being left behind on the analog backup line.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

[Explanation of symbols]

 11, 12 ... Modem 13 ... Analog private line 14 ... Analog public line 111, 121 ... Transmitting part 112, 122 ... Receiving part 113, 123 ... Private line interface 114, 124 ... Public line interface 115, 125 ... DTE interface 116, 117 , 126, 127 ... Line interface 118, 128 ... Operation unit 119, 129 ... Control unit

Claims (1)

[Claims] 1. An automatic line restoration device for restoring a communication line connecting two modems from an analog backup line to an analog dedicated line, when a predetermined line switching request occurs, a carrier that stops carrier transmission for a predetermined time. And a line switching unit for switching the communication line from the analog backup line to the analog dedicated line when the predetermined time elapses after the carrier transmission is stopped by the carrier transmission stop unit. An automatic line restoration device characterized in that