JPH02296432A - Supervisory device for disconnection of transmission line - Google Patents

Abstract

PURPOSE:To supervise a broken line with simple constitution and to discriminate the kind of broken line by superimposing a DC component of a prescribed level onto a transmission signal, sending the result, extracting the DC component from a reception signal and discriminating the fact of broken line based on the level. CONSTITUTION:A comparator 7 discriminates the reception data from a reception signal at a receiver side 2. On the other hand, a low pass filter 8 extracts a DC component VF corresponding to a transmission offset voltage VOFS from a reception signal. If a broken transmission line 3 takes place, the DC component VF is deviated from a range between threshold levels V2 and V3 are signals L1, L2 go both to an L level. The level of the reception signal is increased to nearly twice in the open state and the DC component VF takes a value close to 2VOFS, then both the signals L1, L2 go to an H level. Then based on the signals L1, L2 as shown in figure, the control section classifies the cases into the said three patterns.

Description

[Detailed description of the invention] A. Bone for industrial use! i! f The present invention relates to a device for monitoring disconnections in a transmission line.

B1 Overview of the Invention The present invention superimposes a DC component at a certain level on a transmission signal for transmission, extracts the DC component from the received signal, and determines whether a wire is disconnected based on the level, thereby preventing wire disconnection with a simple configuration. It is possible to monitor the wire breakage and also to determine the type of wire breakage.

C1 Prior Art In general, loop transmission devices are configured to switch systems and perform loopback when an abnormality occurs in the transmission line, and are equipped with a device to monitor disconnection of the transmission line.

Conventional monitoring devices monitor disconnections by adding a specific pattern (flag) to transmission data and monitoring reception of the flag.

In addition, when the transmission data is transmitted by carrier modulation, there is also a mode in which disconnection is monitored by monitoring reception of the carrier.

D Problems to be Solved by the Invention However, the above conventional configuration requires a circuit configuration for specific pattern detection or carrier detection;
There was a problem with the equipment, which made it more complicated.

The present invention has been made in view of this problem, and its purpose is to provide a wire breakage monitoring device that can be realized with a simple circuit configuration and is capable of determining the type of wire breakage. .

Means for Solving Problem E1 In order to achieve the above object, the present invention provides a transmission line disconnection monitoring device comprising the following means.

That is, the following means are provided on the transmitting side.

■ A DC component superimposition section that superimposes a constant level DC component onto the transmission signal.

■ A current amplification unit that sends the output of the DC component superimposition unit to the transmission line.

In addition, the following means are provided on the receiving side.

■ Transmission signal extraction section that extracts the transmission signal from the received signal.

■ A filter that extracts the DC component from the received signal.

■ A disconnection detection section that detects disconnection based on the output level of the filter. This disconnection detection unit determines that the transmission line has been disconnected at the previous stage of the receiving side based on the low output level, and determines that the transmission line has been disconnected at the downstream stage of the receiving side due to the high output level. Ruchino.

F Work 111 According to the present invention, a DC component of a constant level is superimposed on a transmission signal to perform one transmission. That is, on the transmitting side, the DC component is superimposed on the transmission signal and transmitted, and on the receiving side, the transmission signal is extracted from the received signal, thereby transmitting and receiving the transmission signal.

Disconnection on the receiving side is monitored by extracting a DC component from the received signal using a filter and checking the level of the DC component using a disconnection detection section. In other words, depending on the output level of the filter, the type of disconnection in the transmission line,
In other words, it is determined whether the disconnection location is in the front or rear stage of the receiving side.

G. Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows a transmission device according to an embodiment of the present invention.

The transmitting side 1 and the receiving side 2 are for data transmission, and a transmission path 3 is provided between the bolts of both.

On the transmitting side l, an adder 4 applies a transmission offset voltage V to the transmission data TXD. This is to superimpose FS. The current amplifier 5 amplifies the output of the adder 4 and transmits it to the transmission line 3.

The transmission line 3 is composed of a pair of wires. R is a terminating resistor.

On the receiving side 2, the receiving amplifier 6 receives the transmission signal from the transmission line 3. Comparator 7 is thread,
The received data RX l) is discriminated from the output of the receiving amplifier 6 based on the hold voltage ■1.

The low-pass filter 8 removes noise and the like from the output of the receiving amplifier 6 and extracts a DC component. The comparator 9 compares the output of the low-pass filter 8 with the voltage V, and outputs a signal I71 when the former exceeds the voltage V. The comparator IO compares the output of the low-pass filter 8 with the threshold voltage 3, and outputs a signal when the former exceeds the latter. Signal I75. L, is output to a control section (not shown) that determines whether the wire is disconnected.

Here, with reference to FIG. 2, the state of the transmission line 3 when it is abnormal will be explained.

For one transmitter l, there are two receivers 2 (RXi, R
X2). On the transmitting side 1, the transmitting offset voltage ■. , 5, so if the transmission line 3 is disconnected between the receiving side RXI and RX2, the resistance R7 on the receiving side RX1 becomes infinitely large, and the resistance increases. The current flowing through R is doubled, and the reception level becomes 2 oFg. This is called an open state. Further, on the receiving side RX2, no current flows due to the disconnection, and the reception level becomes O.

This is called the Nyoto state.

Figure 3 shows the transmission offset voltage ■. The relationship between F, 3 and threshold voltages V, , V, , V3 is shown.

As shown in this figure, the threshold voltage ■1 is
The transmit offset voltage V is used to distinguish the received data RXD from the received signal. , slightly higher than S (set (
Figure 4(a) Reference 1j, :4). Also, threshold voltage V7. V is the transmission offset.

1-? Ti pressure V. Determine the upper limit and limit of the allowable range of the output of the low-pass filter 8 corresponding to F5 (see Fig. 4(C)), and V3<VoFs<Vt<2.
■It is set in the relationship of θFg.

FIGS. 4(a) to 4(e) show waveforms of each part of the present transmission device during normal operation.

The reception signal received from the transmission path 3 has a transmission offset voltage (■) in the transmission data (pulse signal), as shown in FIG. The waveform is a superimposed FS.

On the receiving side 2, as shown in FIG. 2(b), a comparator 7 discriminates received data from the received signal.

On the other hand, the low-pass filter 8 extracts a DC component (1) corresponding to the transmission offset voltage Vors from the received signal, as shown in FIG.

In the normal case, this DC component 1 takes a value between the threshold voltages V, , V5, so in the same figure (cl) (
As shown in e), the signal becomes L (0-) level, and the signal becomes [1 (high) level.

If a disconnection occurs in transmission line 3, DC component ■.

is out of the range between the Threno/Nihold voltages V, , V3, and the signal changes to 1.117t. In other words, in 'i: I-to-shaped jfJ, the DC component ■ takes a value close to 0 and becomes lower than the threshold pressure u pressure ■3, so the signal
, L, are both at L level. Also, in an open state,
As shown in FIGS. 5(a) to 5(d), the level of the received signal is about twice as high as that of the received signal, and the DC component (2) takes a value close to 2VOFS, so the DC component (2).

becomes higher than the thread and current voltage ■2, and the signal Ll
, L2 both become H level.

In this embodiment, as shown in FIG. 6, the control section divides the signals 1-L2 into the above three patterns.

As described above, this embodiment has the advantage that it is possible to detect not only whether or not there is a break in the transmission line, but also whether the break point is in the front stage or the rear stage.

In addition, since it is sufficient to judge the level of the DC component, the low-pass filter 8 and the comparator 9. t.

This has the advantage that it is possible to construct a simple monitoring device consisting of: Furthermore, by making the time constant of the low-pass filter 8 sufficiently large, it is possible to avoid false detection due to noise, which has the advantage of improving reliability.

Furthermore, by using the current amplifier 5 as a transmitter on the transmitting side 1, there is an advantage that overcurrent can be prevented when the transmission line 3 is short-circuited.

As described in detail of the H0 invention, according to the present invention, by checking the level of the DC component output by the filter using the disconnection detection section, the disconnection state can be classified as 'I'll, so that the flag is not flagged as in the conventional method. Compared to configurations that perform detection or carrier detection, this has the advantage of requiring a simple circuit configuration.

Further, there is an advantage that it is possible to distinguish whether there is a disconnection or not and the type of disconnection, that is, whether the disconnection is located before or after the receiving side, depending on the level of the DC component output from the filter.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a transmission device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the state of the transmission line when abnormality occurs, and Fig. 3 is a transmission offset voltage and each thread no-hold voltage. Explanatory diagram showing the relationship, Figures 4(a) to (e)
1 is a waveform diagram of each part of the transmission device in the normal state, FIGS. 5(a) to 5(d) are waveform diagrams in the open state, and FIG. 6 is a chart showing the λ standard for determining a disconnection state. . 1... Sending side, 2... Receiving side, 3... Transmission path, 4...
・Adder, 5 ・Current amplifier, 6 ・Reception amplifier, 7 ・
Reception cheater discrimination t Lufun parator, 8...Low pass filter, 9 ・Threnon hold voltage V21 limit value)
10... A comparator that performs comparison based on threshold voltage V (lower limit value). Figure 2: Transmission path abnormality status Figure 3: Relationship between transmission offset voltage and each threshold voltage Figure 6: Criteria for determining disconnection status

Claims (1)

[Claims] (1) In a device that monitors disconnections in a transmission line, a DC component superimposition unit that superimposes a DC component at a certain level on a transmission signal;
A current amplification section for transmitting the output of the DC component superimposing section to the transmission path is provided on the transmission side, a transmission signal extraction section for extracting the transmission signal from the reception signal, a filter for extracting the DC component from the reception signal, and a filter for extracting the DC component from the reception signal. It detects a disconnection based on the output level, and if the output level is low, it determines that the transmission line has been disconnected at the previous stage of the receiving side, and
1. A transmission line disconnection monitoring device comprising a disconnection detection unit on a receiving side that determines that the transmission line is disconnected at a stage subsequent to the receiving side based on a high output level.