JPH08191338A - Method and device for monitoring transmission line - Google Patents

Abstract

PURPOSE: To provide a method and device for monitoring plural transmission lines in order by a single monitoring system under time-division control when the transmission lines are monitored batchwise. CONSTITUTION: This device is equipped with a time-division control part 52 which performs the time-division control so that specific monitor times are allocated to the transmission lines in order, a monitor set part 50 which inserts an input-side monitor value, etc., into digital signals inputted to the transmission lines after the monitoring times are assigned, and a monitor detection part 51 which extracts the input-side monitor values, etc., from the digital signals outputted from the transmission lines, collates the input-side monitoring values, etc., with the output-side monitoring values, etc., by a specific method, and outputs an alarm as to a transmission line which is abnormal in collation result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line monitoring method and apparatus for collectively monitoring a plurality of transmission lines with a single monitoring system.

The present invention can be used particularly as a monitoring system for a digital signal processing device, and for example, each of a plurality of data buses (including interface circuits) for connecting devices or packages in the device is individually provided. It is effective when monitoring.

[0003]

2. Description of the Related Art FIG. 17 schematically shows a configuration example of a conventional in-apparatus monitoring system. For example, when the package A and the package B are connected by the data bus 62 in a certain device, the data bus 62 is monitored by providing the data monitoring circuit 60 on the package A side and the check circuit 61 on the package B side. It can be performed. For example, the following monitoring methods are available.

Monitoring Method by BIP Calculation In the monitoring circuit 60, a BIP (Bit Interleaved Parity;
Bit interleaved parity) operation is performed and the operation result is inserted into the next frame, while the check circuit 61 similarly performs BIP operation for each frame of the signal output from the data bus 62, This is a method of comparing the operation result with the operation result of the monitoring circuit 60 extracted from the next frame, and judging the state of the data bus 62 depending on whether or not both operation results match. Monitoring by CRC calculation Instead of the above BIP calculation, CRC (Cyclic Redundanc)
y Check: Cyclic redundancy check) This is a method of performing an operation. Monitoring by PATH pattern detection In the monitoring circuit 60, a PATH pattern (a fixed bit pattern determined according to the device specifications) is inserted into each frame of the signal input to the data bus 62, while in the check circuit 61, the data bus is inserted. In this method, the bit pattern extracted from each frame of the signal output from 62 is compared with the PATH pattern, and the state of the data bus 62 is determined by whether or not the patterns match. Monitoring by PN pattern detection The monitoring circuit 60 generates a PN pattern (pseudo random pattern) and inserts the PN pattern into each frame of the signal input to the data bus 62, while the check circuit 61 uses the data bus. This is a method of judging the state of the data bus 62 by performing a code error check on the bit pattern extracted from each frame of the signal output from 62 by detecting the PN pattern of the synchronous pull-in type. Monitoring by detection of input loss of data is a method of monitoring only by the check circuit 61 on the package B side.
This is a method of inspecting the input disconnection monitoring bit of the signal output from the device, and determining that a failure has occurred in the data bus if the bit shows an abnormal value.

[0005]

In the case of monitoring the transmission lines between the devices or the packages in the device by the above method, conventionally, the same number of monitoring systems as the number of the transmission lines (the monitoring circuit 60 in the above example is used. And check circuit 61) is required,
As the number of transmission lines increases, the circuit scale and power consumption increase.

The present invention has been made in view of the above problems, and an object thereof is to provide a method and apparatus for sequentially monitoring a plurality of transmission lines by a single monitoring system by time division control.

[0007]

1 and 2 are explanatory views of the principle according to the present invention. FIG. 1 shows an apparatus configuration in the case of performing monitoring by calculation or pattern detection on a transmission line.

In FIG. 1, a monitoring setting unit 50 is connected on the signal input side and a monitoring detection unit 51 is connected on the signal output side to the transmission lines 1 to n, and a time division control unit 52 is connected to the monitoring setting unit 50 and the monitoring detection unit. Each is connected to the section 51.

The time division control section 52 sends a transmission path selection signal to each of the monitoring setting section 50 and the monitoring detection section 51.
This transmission path selection signal is a signal instructing to sequentially select the transmission paths 1 to n for a predetermined time.

In the case of performing monitoring by calculation, for example, the monitoring setting unit 50 may use the transmission path i while the transmission path i is selected.
Predetermined calculation (for example, BIP calculation, CRC calculation, etc.) based on the contents of a predetermined section of the digital signal input to
Is performed to calculate the input side monitoring value, and the input side monitoring value is written in a predetermined bit position after the section. On the other hand, the monitoring detector 51 calculates the output-side monitoring value by performing the above calculation based on the content of the predetermined section of the digital signal output from the transmission path i while the transmission path i is selected. , The input side monitoring value is read from a predetermined bit position after the section, the input side monitoring value is compared with the output side monitoring value, and when both values do not match, an alarm is output for the transmission path i.

In the case of monitoring by pattern detection, for example, the monitoring setting unit 50 specifies a specific method at a predetermined bit position of a digital signal input to the transmission path i while the transmission path i is selected. The bit pattern (for example, PATH pattern, PN pattern, etc.) generated in step 3 is written. On the other hand, the monitoring detector 51 reads a bit pattern from the predetermined bit position of the digital signal output from the transmission path i while the transmission path i is selected, and determines whether or not there is a code error in the bit pattern. Inspect by method
When a code error is detected, an alarm is output for transmission line i.

FIG. 2 shows an apparatus configuration for monitoring the transmission line by detecting an input disconnection. In FIG. 2, the input disconnection monitoring unit 53 is provided on the signal output side for the transmission lines 1 to n.
Are connected, and the input disconnection monitoring unit 53 is connected to the time division control unit 52.

The time division control section 52 sends the above-mentioned transmission path selection signal to the input disconnection monitoring section 53. For example, while the transmission line i is selected, the input disconnection monitoring unit 53 inspects the digital signal output from the transmission line i, and outputs an alarm for the transmission line i when the input disconnection is detected.

[0014]

FIG. 3 is a time chart showing an example of time-division control for monitoring the transmission lines 1 to n. In this example,
According to a transmission path selection signal from the time division control unit 52, a constant monitoring time T is sequentially assigned to the transmission paths 1 to n, and the transmission paths are assigned while the monitoring time T is assigned to each transmission path. The signal D flowing is monitored. That is, in one monitoring cycle, the signal D ₁₁ of the transmission line 1 at the monitoring time T ₁ , the signal D ₂₂ of the transmission line 2 at the monitoring time T ₂ , the signal D _{33 of} the transmission line 3 at the monitoring time T ₃ , ... ,
At the monitoring time T _n , the signals D _{nn on the} transmission line n are monitored, and this cycle is repeated.

FIG. 4A shows an operation example of monitoring by calculation. At the monitoring time T _i in which the transmission path i is selected, the section b _{XX to} b _YY of the signal D _ii on the input side of the transmission path i.
The input-side monitoring value is calculated based on the contents of the above, and the input-side monitoring value is inserted into the bit position b _ZZ of the signal D _ii . Further, the output side of the transmission line i is calculated output monitoring value based on the contents of the section b _XX ~b _YY signal D _ii, extracted from the bit position b _ZZ of the output-side monitor value and the signal D _ii The monitoring value on the input side is compared, and if these two monitoring values do not match, an alarm ALMi for the transmission line i is output.

FIG. 4B shows an operation example of monitoring by pattern detection. In monitoring time T _i of the transmission line i is selected, the input side of the transmission line i is the bit position b _XX ~b _YY signal D _ii, the bit pattern which is generated in a predetermined manner is inserted. Also, on the output side of the transmission line i, the signal D
_A bit pattern is extracted from the bit positions b _{XX to} b _{YY of ii} , and the presence or absence of a code error occurring in the bit pattern on the transmission path i is checked. When a code error is detected, the alarm ALMi for the transmission line i is output.

FIG. 4 (c) shows an example of the operation of monitoring by detecting an input break. Monitoring time T when transmission line i is selected
_{In i} , the output side of the transmission line i is inspected for the input disconnection of the signal D _ii , and when the occurrence of the input disconnection is detected, the alarm ALMi for the transmission line i is output.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. In the embodiment described below, a failure occurring in n data buses (including interface circuits in the middle) connecting devices or packages in the device is monitored. As shown in FIG. 5A, it is assumed that digital signals that are frame-synchronized with each other at a frame repetition frequency of 8 kHz (frame cycle 125 μsec) are flowing through these n data buses.

In the following embodiments, the n data buses are sequentially monitored one by one, but a monitoring time of 1 msec is assigned to each data bus. Therefore, FIG.
As shown in (b), data obtained by sequentially extracting data from each data bus in units of 8 frames is to be monitored.

However, the signal form of the data, the monitoring time, and the like shown here are merely examples, and various modes are possible according to the case in implementing the present invention.

FIG. 6 shows an example of a time-division control section for realizing the above-mentioned time-division control. As shown in FIG. 6A, the time division control unit 1 outputs n select signals corresponding to each data bus. As shown in FIG. 6B, the n select signals are sequentially set to the H level for 1 msec one by one from the select signal for the data bus 1 to the select signal for the data bus n. Therefore, if the data bus corresponding to the select signal outputting the H level is selected and the data bus is monitored while the select signal is at the H level, n
The data bus 1 to the data bus n can be sequentially monitored for 1 msec each with [msec] as one cycle.

FIG. 7 shows an embodiment of the present invention. The present embodiment is a transmission line monitoring device that monitors by BIP calculation. The configuration of the apparatus of this embodiment has n data buses (transmission paths), the data input side is the monitoring setting side, and the data output side is the monitoring detection side.

A time division circuit 2 and a BIP operation circuit 3 are provided on the monitor setting side. Each of n data buses is connected to the time division circuit 2 and the BIP operation circuit 3, and the output of the time division circuit 2 is BIP. It is connected to the input of the arithmetic circuit 3. on the other hand,
A time division circuit 4 and a BIP operation comparison circuit 5 are provided on the monitoring detection side, each of the n data buses is connected to the time division circuit 4, and the output of the time division circuit 4 is input to the BIP operation comparison circuit 5. It is connected. Further, the above-mentioned n select signals are supplied to the time division circuit 2 and the time division circuit 4 from the time division control unit 1 not shown.

The time division circuit 2 on the monitor setting side sets n data buses to one in accordance with a select signal from the time division control unit 1.
Books are sequentially selected one by one, and data for eight frames are taken out from the selected data bus and input to the BIP arithmetic circuit 3. The BIP calculation circuit 3 executes BIP calculation based on the contents of each input frame. The setting side calculation result calculated by the BIP calculation circuit 3 is inserted into the frame next to the frame that is the calculation target through the calculation result insertion unit 12.

The time division circuit 4 on the monitoring and detection side takes out 8 frames of data from the data bus selected according to the select signal from the time division control unit 1 through the operation result extraction unit 13 and inputs it to the BIP operation comparison circuit 5. To do. BIP
The operation comparison circuit 5 executes the BIP operation based on the contents of each input frame to calculate the inspection side operation result, and further extracts the setting side operation result from the next input frame and sets the setting side operation result. And the detection side inspect whether the calculation results match. If the calculation results do not match, an alarm signal is output. In this case, the alarm signal is serially output corresponding to the frame.

FIG. 8 is a time chart specifically showing the operation of this embodiment described above. The figure shows the operation at the timing immediately after the monitoring target is switched from the data bus 1 to the data bus 2. On the monitor setting side, BIP calculation is performed based on the contents of frame 1 of data bus 2, and the calculation result is inserted into a predetermined phase (bit position) of frame 2. On the other hand, the monitoring detection side also performs a BIP operation based on the contents of frame 1 of data bus 2 and compares the operation result with the operation result inserted in frame 2. If they do not match, an alarm signal for data bus 2 is issued. Is output.

For the two frames that cross the boundary of data bus switching, the calculation target and the calculation result are sent from the monitoring setting side to the monitoring detection side through separate data buses, so that the calculation result does not match on the monitoring detection side. Even if it is detected, it cannot be determined which data bus has a failure. However, in general, when a failure occurs in the data bus, mismatches in the calculation results occur continuously, so it is possible to judge from the context. For example, if there is a mismatch in the operation result in the comparison between the last frame of the data bus 1 and the first frame of the data bus 2, if a mismatch in the operation result is detected immediately before that, the data bus 1 It can be determined that there is a failure, or if a mismatch in the operation results is detected immediately thereafter, it can be determined that there is a failure in the data bus 2.

The alarm signal is more practical to be output when a predetermined number of consecutive occurrences of a mismatch in the operation results for a certain data bus are output, rather than immediately.

FIG. 9 shows another embodiment of the present invention.
In this embodiment, a time division circuit 6 is further added after the BIP operation circuit 5 of the device of the embodiment shown in FIG. Contrary to the time division circuits 2 and 4, the time division circuit 6 is a circuit that expands the time division serial data into n parallel data, and inputs the serial alarm signal from the BIP operation comparison circuit 5, Output as n parallel alarm signals. The time division control unit 1 inputs the select signal 1 to the time division circuits 2 and 4, and inputs the select signal 2 to the time division circuit 6. Although the select signal 1 and the select signal 2 have the same contents, the phase of the select signal 2 is set to the phase of the select signal 1 in consideration of the fact that the signal on the data bus may be delayed a little before reaching the time division circuit 6. It's delayed by more.

FIG. 10 shows an example of serial / parallel conversion of an alarm signal. When a serial alarm signal as shown is input to the time division circuit 6, the time division circuit 6
Parallel alarm output of the data bus 2 and data bus n
The output corresponding to -2 changes from L level to H level.

In the other embodiments described below, the output of the alarm signal can be converted from serial to parallel by the same method.

By the way, in the time division control of the above-described embodiment, a constant cycle n [m is set for each of the n data buses.
Since the monitoring time (1 msec) is assigned in [sec], if a certain data bus has a fault that occurs intermittently in the same cycle, the fault cannot be detected. For example, as shown in FIG. 11A, when a failure occurs intermittently in the data bus 2 at a constant cycle n [msec] and the failure occurs at the same timing as the monitoring time of the data bus 1, This failure of the data bus 2 is never detected.

This problem can be solved by changing the order in which the time division control unit 1 allocates the monitoring time to each data bus for each cycle. For example, as shown in FIG. 11B, the data bus 1, the data bus 2, ...
.., when monitoring is performed in the order of the data bus n, in the next cycle, the data bus n, the data bus 1, the data bus 2, ... In the cycle, the data bus n-1, the data bus n, the data bus 1, ..., The data bus n-3 are monitored in this order, so that the monitoring order of the data buses is cyclically shifted for each cycle. A cyclic shift method or a random method in which the monitoring order of the data buses is randomly changed in each cycle is possible.

The modification of the time division control system is not limited to the above-mentioned special failure on the data bus,
It is also effective when detecting a failure in this device. For example,
When the operation result cannot be correctly inserted only in a specific data bus due to a failure in the time division circuit 2 or the BIP operation circuit 3, the failure location can be found by observing the output state of the alarm signal. This modification of the time division control method can be similarly applied to each of the embodiments described below.

The above description of the embodiment of monitoring by BIP calculation is similarly applied to the case of performing monitoring by CRC calculation.

FIG. 12 shows another embodiment of the present invention. The present embodiment is a transmission line monitoring device for monitoring by detecting a PATH pattern. The configuration of the apparatus of this embodiment has n data buses (transmission paths), the data input side is the monitoring setting side, and the data output side is the monitoring detection side.

A time division circuit 2 and a PATH pattern generation circuit 7 are provided on the monitor setting side, each of the n data buses is connected to the time division circuit 2, and the output of the PATH pattern generation circuit 7 is the time division circuit 2. It is connected to the. On the other hand, the time division circuit 4 and the PATH pattern comparison circuit 8 are provided on the monitoring detection side.
Are provided, each of the n data buses is connected to the time division circuit 4, and the output of the time division circuit 4 is connected to the input of the PATH pattern comparison circuit 8. Also, n select signals are supplied to the time division circuit 2 and the time division circuit 4 from the time division control unit 1 (not shown).

PATH pattern generation circuit 7 on the monitor setting side
Generates a PATH pattern and inputs it to the time division circuit 2. The time division circuit 2 sequentially selects n data buses one by one in accordance with a select signal from the time division control unit 1 and inserts a pattern into a predetermined bit position of each data of 8 frames on the selected data bus. P through section 14
Insert ATH pattern.

The time division circuit 4 on the monitor / detection side takes out 8 frames of data from the data bus selected according to the select signal from the time division control unit 1 through the pattern extraction unit 15 and inputs the data to the PATH pattern comparison circuit 8. .
The PATH pattern comparison circuit 8 compares the PATH pattern inserted in each frame with the correct PATH pattern, and outputs an alarm signal if the comparison results do not match.

FIG. 13 is a time chart specifically showing the operation of this embodiment described above. On the monitor setting side, P
An ATH pattern is generated, and the PATH pattern is inserted in a predetermined phase (bit position) of each frame of the selected data bus. On the other hand, on the monitoring detection side, the PA inserted on the monitoring setting side in each frame of the selected data bus
TH pattern and PATH preset on the monitoring detection side
The pattern is compared, and if they do not match, an alarm signal for the data bus is output.

Since the PATH pattern is a fixed pattern determined by the device specifications, it is not necessary to perform time division control on the monitor setting side. Therefore, as shown in FIG. 14, it is also possible to eliminate the time division circuit 2 from the monitor setting side for the sake of circuit simplification and directly connect the PATH pattern generation circuit 7 to each of the n data buses. In this case, the PATH pattern is inserted into all the frames on the n data buses regardless of the monitoring cycle.

FIG. 15 shows another embodiment of the present invention. The present embodiment is a transmission line monitoring device that monitors by detecting a PN pattern. The device of this embodiment is the PAT of FIG.
Although it has the same configuration as that of the embodiment apparatus by H pattern detection, a PN pattern generation circuit 9 is provided instead of the PATH pattern generation circuit 7 on the monitoring setting side, and a PN pattern instead of the PATH pattern comparison circuit 8 on the monitoring detection side. The difference is that the check circuit 10 is provided.

The PN pattern generating circuit 9 on the monitor setting side is set to P
An N pattern is generated and input to the time division circuit 2. The time division circuit 2 sequentially selects n data buses one by one according to a select signal from the time division control unit 1,
The PN pattern is inserted into the predetermined bit position of each of the data of 8 frames on the selected data bus through the pattern inserting unit 14.

The time-division circuit 4 on the monitor / detection side takes out 8 frames of data from the data bus selected according to the select signal from the time-division control unit 1 through the pattern extraction unit 15 and inputs it to the PN pattern check circuit 10. . The PN pattern check circuit 10 performs a sync pull-in PN pattern detection for each input frame, and outputs an alarm signal when a code error is detected.

FIG. 16 shows another embodiment of the present invention. The present embodiment is a transmission line monitoring device that monitors by detecting a data input break. This embodiment differs from the other embodiments described above in that the data output side of the n data buses (transmission paths) is the monitoring detection side, and monitoring is performed only on the monitoring detection side.

An input break detection bit is provided in each frame of data flowing through the data bus, and the input break detection bit is always kept at a constant value (for example, H level) unless a data input break occurs. There is.

A time division circuit 4 and a data input disconnection detection circuit 11 are provided on the monitoring detection side. Each of the n data buses is connected to the time division circuit 4, and the output of the time division circuit 4 is a data input disconnection monitor. It is connected to the input of the circuit 11. Also, n select signals are supplied to the time division circuit 4 from the time division control unit 1 (not shown).

The time division circuit 4 sequentially selects n data buses one by one in accordance with a select signal from the time division control unit 1, takes out 8 frames of data from the selected data bus, and detects a data input disconnection. Input to the circuit 11. The data input break detection circuit 11 checks whether the input break detection bit is kept at a predetermined value for each input frame, and when the input break detection bit shows an abnormal value, an alarm signal is output. Output.

The implementation of the present invention is not limited to the method using the calculation and pattern detection shown in each of the above-described embodiments, and the same applies to other methods such as other calculation and pattern detection. The effect can be obtained.

[0050]

As described above, according to the present invention,
Since multiple transmission lines can be sequentially monitored by a single monitoring system by time-division control, there is no need to individually provide monitoring systems for the number of transmission lines to be monitored, unlike the conventional case.
It greatly contributes to the reduction of circuit scale and power consumption.

[Brief description of drawings]

FIG. 1 is a principle explanatory view (1) according to the present invention.

FIG. 2 is a principle explanatory view (2) according to the present invention.

FIG. 3 is a time chart for explaining time division control of monitoring.

FIG. 4 is a diagram for explaining an operation example of the present invention.

FIG. 5 is a diagram showing a signal form of a data bus in the embodiment of the present invention.

FIG. 6 is a diagram for explaining a time division control unit commonly used in the embodiments of the present invention.

FIG. 7 shows an example of monitoring by BIP calculation.

FIG. 8 is a time chart for explaining a monitoring operation by BIP calculation.

FIG. 9 is another embodiment for monitoring by BIP calculation.

FIG. 10 is a time chart showing an example of serial / parallel conversion of an alarm signal.

FIG. 11 is a time chart for explaining a modified example of the time division control method.

FIG. 12 is an example of performing monitoring by detecting a PATH pattern.

FIG. 13 is a time chart for explaining a monitoring operation by detecting a PATH pattern.

FIG. 14 is another embodiment for performing monitoring by detecting a PATH pattern.

FIG. 15 is an example of monitoring by detecting a PN pattern.

FIG. 16 is an embodiment in which monitoring is performed by detecting input disconnection of data.

FIG. 17 is a diagram showing an outline of a conventional example.

[Explanation of symbols]

 1 time division control unit 2, 4, 6 time division circuit 3 BIP operation circuit 5 BIP operation comparison circuit 7 PATH pattern generation circuit 8 PATH pattern comparison circuit 9 PN pattern generation circuit 10 PN pattern check circuit 11 data input disconnection detection circuit 12 operation Result insertion unit 13 Calculation result extraction unit 14 Pattern insertion unit 15 Pattern extraction unit

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Masahiro Agata 3-28-1 Joto, Oyama-shi, Tochigi Prefecture Fujitsu Digital Technology Limited (72) Shoji Nakamura 3-28-1 Joto, Oyama-shi, Tochigi Prefecture No. Fujitsu Digital Technology Limited (72) Inventor Mitsuru Kurabe 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Within Fujitsu Limited

Claims (4)

[Claims] 1. A transmission line monitoring method for collectively monitoring a plurality of transmission lines, wherein time-division control is performed such that a predetermined monitoring time is sequentially assigned to the plurality of transmission lines, and the monitoring time is assigned. A transmission line monitoring method for performing a predetermined monitoring process on a signal of the transmission line, and outputting an alarm for the transmission line in which an abnormality is detected in the monitoring process. 2. A transmission line monitoring apparatus for collectively monitoring a plurality of transmission lines through which digital signals are transmitted, wherein time division control is performed so that a predetermined monitoring time is sequentially assigned to the plurality of transmission lines. With respect to the time division control unit to perform and the transmission path to which the monitoring time is assigned, the input side monitoring value is calculated by performing a predetermined calculation based on the content of a predetermined section of the digital signal input to the transmission path. A monitoring setting unit that inserts the input-side monitoring value at a predetermined bit position after the section, and a transmission path to which the monitoring time is assigned, based on the content of the predetermined section of the digital signal output from the transmission path. The output side monitoring value is calculated by performing a predetermined calculation, the input side monitoring value inserted at a predetermined bit position after the section is extracted, and the input side monitoring value and the output side monitoring value are compared. And both values Transmission line monitoring apparatus and a monitoring detector which outputs a warning about the transmission line is abnormal engagement. 3. A transmission line monitoring device for collectively monitoring a plurality of transmission lines through which digital signals are transmitted, wherein time division control is performed so that a predetermined monitoring time is sequentially assigned to the plurality of transmission lines. A time division control unit for performing the monitoring, a monitoring setting unit that inserts a bit pattern generated by a predetermined method into a predetermined bit position of a digital signal input to the transmission line for the transmission line to which the monitoring time is assigned, For the transmission path to which the monitoring time is assigned, the bit pattern inserted in the predetermined bit position of the digital signal output from the transmission path is extracted, and the presence or absence of a code error in the bit pattern is inspected by a predetermined method. A transmission line monitoring device including a monitoring detection unit that outputs an alarm for a transmission line in which a bit pattern bit error has occurred. 4. A transmission line monitoring device for collectively monitoring a plurality of transmission lines through which digital signals are transmitted, wherein time division control is performed so that a predetermined monitoring time is sequentially assigned to the plurality of transmission lines. A time-division control unit that performs the monitoring, and an input disconnection monitoring unit that inspects the digital signal output from the transmission line for which the monitoring time is assigned and outputs an alarm for the transmission line where the input disconnection is detected. Equipped transmission line monitoring device.