JPH0413992A - Crossing/approach detector - Google Patents

Abstract

PURPOSE:To eliminate attenuation of receiving level in the longitudinal direction by detecting crossing movement or access of a moving object by amplitude variance of far ends combining signal or near ends combining signal. CONSTITUTION:Receivers 3 and 9 for near ends combining signal and far ends combining signal, are provided at each end of an open typed coaxial cable 2, respectively. The output signals of those receivers 3 and 9 are judged by a judging unit 10 and therewith crossing movement or access of a moving object is detected by the fact that whether one of amplitude, the amplitude and phase, or the square sum of the amplitude and the phase, of the received signals, stays within a predetermined range of standard value or not. In this way, detection sensitivity does not attenuate in a longitudinal direction of the detector, influence by insensible point can be eliminated at any point of which longitudinal position differs, and finally stable sensitivity can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention detects the movement of a moving object such as a person or car crossing between two adjacent detection lines, or the movement of a moving object approaching this detection line. Concerning crossing/approaching detectors.

[Conventional technology]

Conventionally, a detector is known from, for example, Japanese Patent Laid-Open No. 52-123897, which detects intrusion by installing a detection line at an appropriate location such as around a house, and when a person, vehicle, etc. approaches the detection line. There is.

The detector according to this publication is shown in FIGS. 12(a) and 12(b).

(Figure 81 shows a transmission type detector with a transmitter 3 and receiver 4 connected to both ends of the detection line 1', and figure (b) shows a transmitter and receiver 4 connected to both ends of the detection line 1'. Transmitter/receiver 3'
This is a reflection type detector in which a non-reflection terminator 6 is connected to the other end. A transmission line that leaks radio waves is used as the detection line 1'. 5 is a moving object.

In the above detector, when a person approaches the detection line 1', the signal level transmitted from the transmitter to the receiver changes, and the approaching person is detected based on this change.

[Problem to be solved by the invention]

In the above-mentioned type of detector, the transmitter and receiver are directly connected, so the reception level is strong.On the other hand, the amount of change in the reception level due to the approach of an approaching person is extremely small, so the approaching person can be detected by the detection line. The signal level does not change unless you get very close to the line, and the detection range is limited to a cylindrical area with a very small constant radius centered on the detection line.

Therefore, as a way to widen the detection range mentioned above, if the detection line connected to the transmitter and the detection line connected to the receiver are separated, the transmitter and receiver are not directly connected, so regardless of the presence or absence of an approaching person, It is clear that since the reception level becomes weaker, the approach of an approaching person can be detected even if the person is at a certain distance from the detection line, and the detection zone also becomes a thick and wide band-shaped space.

In order to confirm whether the above method is practicable from this point of view, we conducted an experiment using a detector with the following configuration. In other words, it is a detector in which a transmitter and a receiver are installed at one end of two parallel open coaxial cables placed a predetermined distance apart.
The near-end coupling between the coaxial cables allows the detection of the transverse movement of a moving object.

The above-mentioned crossing/approach detector will be explained with reference to FIGS. 13 to 15.

As shown in FIG. 13, this crossing/approach detector connects a transmitter 3 and a receiver 4 to one end of an open coaxial cable 1.20 that is provided at a predetermined distance d (for example, 1 m) from each other. The other end is connected to a non-reflection terminator 6.7 which absorbs the transmitted signal without reflecting it. 5 is a moving object.

The two open coaxial cables 1.2 each have most of the transmitted energy within the coaxial cable, but some of it is also carried in the space outside the cable in the form of surface wave mode or radiation mode. Therefore, near-end coupling occurs between the two open coaxial cables 1.2 provided a predetermined distance apart, such that the signal transmitted from the transmitter 3 reaches the receiver 4, as shown by the dotted line. The reception level of the near-end coupling reaching the receiver 4 is herein referred to as Vco.

In the middle of the two open coaxial cables 1.2 in Figure 13,
If a person walks from the left side (Z = O) to the right side (Z = 1) in the figure, and during that time, for example, a signal of several tens of MHz is transmitted from the transmitter 3 and received by the receiver 4, the level of the received signal is The changes are shown in Figure 14.

As can be seen from this figure, in the region where Z<0, that is, the near-end coupling of the open coaxial cable facing the person is not affected, the signal of the bell is constant. has been received. However, Z
〉70 That is, when a person enters an area that affects the near-end coupling of the facing open coaxial cable, a phenomenon occurs in which the received signal level V of the receiver 4 fluctuates at a constant period, and this received signal level V The amplitude decreases as the moving object moves away from the transmitter side.

On the other hand, this time, we will cross the two open coaxial cables in the X direction and find the position Z where the reception level is maximum at the 14th circle.
= a, the minimum z = b, the same value as y co
When the level of the received signal is measured at each position of c, it changes as shown in FIGS. 15(a) to 15(c). As can be seen from this figure, at position Z = a, the reception level is maximum in the middle of the two open coaxial cables, at position z = b, the reception level is minimum, and at position Z = c, the reception level is maximum. The level hardly changes.

In this way, it is theoretically possible to detect a moving object moving across the X direction at any position along its length with the crossing detector based on the experiment described above. The amplitude decreases as you move from the transmitter to the far end, so if the amplitude exceeds a certain level,
If this is considered as an approach, the detection sensitivity will be low at this far end and some of the above-mentioned blind spots will occur, so there are problems in putting this into practical use.

As a method for solving the problem of the amplitude decreasing, a second experiment using a detector having the configuration shown in FIG. 16 was further attempted. As shown in the figure, two open coaxial cables 1.2 with different phase constants are provided in parallel with each other at a predetermined distance d, and a transmitter 3 is attached to one end of the cable 1, and a transmitter 3 is attached to the other end of the cable 1. A non-reflection terminator 6 is connected to the cable 2, a non-reflection terminator 8 is connected to the end near the transmitter 3, and a receiver 9 is connected to the far end of the cable 2.

According to the detector with the above configuration, the reception level when a person walks in the middle of the two open coaxial cables 1.2 from Z-0 toward Z-l is the same as in the first experimental example. different, first
As shown in Figure 7, the range of variation is constant, but for the traverse in the X direction at Z = a', Z = b' and Z = c' in Figure F, Figure 15 according to the first experiment changes in the same way.

Therefore, although the second experimental example makes it possible to eliminate the influence of cable transmission loss and make the change in reception level constant in the length direction of the detector, it is still not possible to eliminate the dead point.

This invention was made in view of the current state of the conventional detectors for detecting the intrusion of approaching persons, etc., as described above, and its purpose is to develop it as a crossing/approaching detector based on the above-mentioned first and second experimental examples. Even when detecting the movement of an object moving across or approaching in a direction perpendicular to it at any position along its length, it can be put to practical use by eliminating dead points and without attenuation of the reception level in the length direction. The purpose of the present invention is to provide a crossing/approach detector that can be used.

[Means to solve the problem]

Therefore, in the present invention, as a means for solving the above problem, a transmitter is attached to one end of one of two open coaxial cables having different phase constants, which are provided in parallel and separated by a predetermined distance from each other. Connect a non-reflection terminator to the end of the other cable, and the far end of the other cable far from the transmitter has a receiver for receiving the far-end coupled signal, and the near end of the other cable, which is closer to the transmitter, has a receiver for receiving the near-end coupled signal. the receiver for receiving the far-end combined signal and the receiver for receiving the near-end combined signal, and the amplitude of one of the signals is within a predetermined range with respect to a reference value. A traversing/approaching detector is provided with a determiner for determining whether the object is traversing or approaching, and the traversing/approaching detector detects the traverse movement or approach of a moving object by detecting the amplitude change of the far-end coupling signal or the amplitude change of the near-end coupling by the discriminator. It was adopted.

As another means for solving the above problem, in the first invention, a signal from a transmitter is guided through the one cable in the receiver for far-end coupling reception, and this signal is used. A circuit is provided to cancel the far-end coupled signals of the two open coaxial cables, and the signal from the transmitter is directly guided into the receiver for near-end coupled reception, and this signal is used to cancel the far-end coupled signals of the two open coaxial cables. A circuit for canceling the near-end coupling signal is provided to set the far-end coupling reception level and the near-end coupling signal level to 0, respectively, and the determining device detects a change in the amplitude of the far-end coupling or the near-end coupling, thereby detecting a moving object. It may be configured to detect crossing movement or approach of.

In the crossing/approach detector, unidirectional elements may be connected to both ends of the other open coaxial cable.

As yet another solution, in the first invention, the receiver for receiving the far-end coupled signal and the near-end coupled signal includes an amplitude meter that receives an amplitude component and a phase meter that receives a phase component, respectively; The determiner is a determiner that determines whether the amplitude and phase of the far-end coupled signal and the amplitude and phase of the near-end coupled signal are within a predetermined range with respect to a reference value. It may be configured to detect the traversal movement or approach of a moving object by detecting a change in the moving object.

As yet another solution, in the invention having the above configuration, a sum-of-squares adder is provided for combining the outputs of the amplitude meters and phase meters of the receivers of the far-end coupled signal and the near-end coupled signal. The determiner is provided between an amplitude meter, a phase meter, and the determiner, and the determiner determines whether any of the output signals of the sum-of-squares adder is within a predetermined range with respect to a reference value, It may also be configured such that crossing movement or approach of a moving object is detected by detecting a change in a signal using a determiner.

[Effect]

In any of the inventions configured as described above, the respective signals are received by the receivers for the far-end coupled signal and the near-end coupled signal. When detecting the traverse movement or approach of a moving object using only the near-end coupled signal, the reception level decreases as the distance from the transmitter increases along the length of the detector, and a dead point occurs at a certain position. In the invention, the far-end coupled signal being received at the same time has the maximum value or the minimum value at the insensitive point of the near-end coupled signal, and the received level does not decrease along the length direction, so the near-end coupled signal The transversal movement or approach of the moving object is detected by sending the far-end coupled signal and the signal to the determiner, and the determiner comprehensively determines whether any of the signals is within a predetermined range with respect to the reference value.

In the comprehensive judgment by the above-mentioned judgment device, the second invention is based on the amplitude change of the received signal, the second invention is based on the amplitude or phase change, and the fourth invention is based on the square of the amplitude and phase. Judgment is made based on the change in the summation output.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First to Stream Side (FIGS. 1 to 3) FIG. 1 is a schematic block diagram of a first embodiment of the crossing/approach detector according to the present invention.

The detector of this embodiment consists of two open coaxial cables with different phase constants, 1.
A transmitter 3 is connected to one end of one cable 1 of 2, a non-reflection terminator 6 is connected to the other end, and a transmitter 3 of the other cable 2 is connected.
Receivers 4.9 are connected to ◇:;: on the near side and far side of consists of things.

FIG. 2 shows an example of the actual configuration of the open coaxial cable.

The figure (a) shows a case in which slots 31' are provided in a zigzag pattern in the outer conductor 31 of the cable, and the pitch p of the slots is changed between the slots and the open coaxial cable 1.2.

(b) The figure shows slots, /
This is a case where LJ 1-32' is installed and its slot pitch p is changed between the open coaxial cable 1.2 and the open coaxial cable 1.2.

The figure (C) shows an example in which a part of the outer conductor 33 is cut out by providing a continuous slit 33' along the length direction. In the example shown in (d), the center conductor 34 and the outer conductor 3 are connected as shown in the figure.
This is a case where the change is made between 5 and 5.

Although not shown, there are other examples as follows.

・The insulator that supports between the inner and outer conductors is made of foamed plastic material and the foaming rate is changed.

The outer conductor is made of braid, and the degree of braiding and the braiding pitch are varied.

Next, the operation of the crossing/approach detector of this embodiment configured as described above will be explained.

In the detector of this embodiment, the signal transmitted from the transmitter 3 has a near-end coupling that reaches the receiver 4 and a near-end coupling that reaches the receiver 9, as shown by solid arrows and dotted arrows in FIG. Far-end coupling occurs, respectively.

The changes in the received signal due to the near-end coupling and far-end coupling are explained in the third section.
Shown in Figures (a) and (b). The figure shows the change in received signal level that occurs when a person walks in the middle of two open coaxial cables 1.2 from the left side (Z=O) to the right side (z=p) in Figure 1. The coordinates of the Z-axis are aligned in both figures.

Reception level VCI when no one is present for both receivers 4 and S
, ■It is set so that when there is a certain change in the reception level with respect to c2, it is assumed that a person has crossed the road.

As can be seen from the figure, a dead point occurs at Z=e in the near-end connection in figure (a). However, in the far-end connection shown in FIG. 3(b), a change in the peak occurs at the same position Z=e.

On the other hand, in far-end coupling, a dead point occurs, for example, at the point Z=f, but in near-end coupling at the same position, a peak change occurs.

Therefore, in the detector of this embodiment, in order to increase the detection ability by reducing the dead points at each of the near-end coupling and far-end coupling as much as possible, cross-section detection and near-field detection based on a constant change in reception level at the far-end coupling are performed. The final crossing detection is performed through a judger 10 that comprehensively judges the crossing detection based on a constant change in reception level at the end connection using an OR condition, and this is almost as if the detection abilities of both are combined so as to complement each other. Detection ability can be obtained.

Two Examples (FIGS. 4 to 7) FIG. 4 is a schematic block diagram showing a second embodiment of the detector according to the present invention.

In this embodiment, two open coaxial cables 1.2 with different phase constants are provided a predetermined distance d apart, and a transmitter 3 is installed at one end of one cable 1, and a non-reflection terminator 6 is installed at the other end.
Connect. Also, transmitter 3 is attached to the other cable 2.
Receiver 4 at the near end on the side close to the receiver 9 at the far end on the far side
Connect each.

Then, branchers 11 and 12 are provided at the intermediate positions of the connections to the non-reflection terminator 6 and the receiver 9 on the far end side, respectively.
The signal from 1 passes through an attenuator 13, a phase shifter 14, and is connected to be sent to a receiver 9 via a splitter 12. A similar circuit consisting of a splitter 15, 16, an attenuator 17, and a phase shifter 18 is provided on the near end side.

The circuit between branchers 11 and 12 and the circuit between branchers 15 and 16 each lead a part of the transmitted signal to the receiver and cancel the amount of far-end coupling and near-end coupling so that the receiving power becomes 0. It is installed in

Furthermore, the receiver 4.9 is connected to a determiner 10 that comprehensively determines the crossing detection results based on the signals received by these receivers under an OR condition.

The operation of this embodiment configured as described above is shown in FIG. 5(a).
, (b).

Figures (a) and (b) respectively show the middle of two open coaxial cables from the left side (Z=O) to the right side (Z=O) shown in Figure 4.
When a person walks towards fi), it is the reception level of the receiver 9 that receives far-end coupling and the receiver 4 that receives near-end coupling, and the horizontal axes in both figures are Z-0 in both the upper and lower figures. , Z-l
It is matched as shown in .

The level of both receivers 4 and S when no one is present is 0 (receiver noise level VN), and the voltages at a certain level ■0, ■
It is set so that a crossing is detected when a level higher than t2 occurs.

By the way, with far-end coupling and near-end coupling, depending on the surrounding environment etc., there are dead points where the reception level does not reach a certain level even if a person crosses the far-end coupling, points (a), (b),
Near-end connections occur at points (c), (d), and (e).

In this embodiment, in order to reduce such blind points as much as possible and improve the detection ability, a judger 10 is provided which comprehensively judges crossing detection by far-end coupling and crossing detection by near-end coupling under an OR condition.
Performs final crossing detection through. Therefore, due to the mutually complementary effect of the cross-sectional detection by the far-end coupling and the near-end coupling, the detector can reduce the number of dead points and obtain a certain level of detection sensitivity.

FIG. 6 shows a partially modified embodiment in which a part of the second embodiment is modified, and for the circuit shown in FIG. , 20
The only difference is that .

A unidirectional element is an element that has different transmission characteristics in forward and reverse directions, and can be a unidirectional tube, an amplifier, or the like.

Although the operation of this embodiment is basically the same as that of the second embodiment, it differs slightly in the following points.

FIG. 7 shows the case where the unidirectional element 19.20 is not inserted between the receiver 4.9 and the open coaxial cable 2 ((a),
It shows the difference between the case of insertion (Fig. (B)) and the case of insertion (Fig. (C)). In the figure (a), a part of the transmission signal is transmitted to the near-end receiver 4 as shown by the solid line arrow, but a part of the signal reaches the far end side as shown by the dotted line. This means (
b) As shown in the figure, this also applies to the case where a part of the transmission signal is transmitted to the receiver at the far end as indicated by the solid arrow. The solid line indicates that when both attenuators coexist, each attenuator on the far end side and the near end side, the attenuator by a phase shifter, and phase adjustment mutually influence the other end.

Therefore, in this embodiment, by inserting unidirectional elements 19 and 20, the signal shown by the dotted line in Figure C1 is blocked at the unidirectional element and does not reach the other end through the open coaxial cable 2. Therefore, each end will not affect the other end.

3. Stream side (Figures 8 to 11) Figure 8 shows a schematic block diagram of a detector according to a third embodiment of the present invention.

The detector of this embodiment consists of two open coaxial cables with different phase constants, 1.
2, a transmitter 3 is connected to one end of one cable 1, and a non-reflection terminator 6 is connected to the other end.

In addition, on the other cable 2, a receiver for far-end coupled signals consisting of an amplitude meter 22 and a phase meter 23 is connected to the far end of the transmitter 3 via a distributor 21, and a distributor 24 is connected to the near end of the transmitter 3. A near-end coupled signal receiver consisting of an amplitude meter 25 and a phase meter 26 is connected therethrough.

A part of the transmission signal from the branch 11 provided at the far end connection part of the cable 1 is sent to the phase meter 23 in the far end example, and similarly, a part of the transmission signal from the branch 15 is sent to the phase meter 26 at the near end. is connected so that a portion of the transmitted signal is transmitted.

Furthermore, the respective outputs of the amplitude meter 22 and phase meter 23 of the far-end coupled signal, and the amplitude meter 25 and phase meter 26 of the near-end coupled signal are connected to the determiner 10. This determiner 10 is a determiner that comprehensively determines whether any of the four signals mentioned above exceeds a certain standard (reception level).

The operation of the detector of this embodiment configured as described above is explained in the ninth section.
This will be explained based on FIGS. (a), (b), (C), and (d).

When a person walks along the open coaxial cable in the center from Z-〇 to Z=1, the receiver at the far end receives the signal shown in Figure 9 (a).
) and (b), the amplitude and phase of the received signal change.

As can be seen from the figure, when the amplitude is at the dead point level, the phase shows the maximum value or the minimum value.

Therefore, when a person crosses or approaches the detector at any position in the length direction, even if that position is an amplitude dead point, the discriminator 10 detects the crossing or approach of a moving object due to the phase change. be able to.

The above effect is the same for near-end coupling as shown in FIGS. 9(C) and 9(d).

Therefore, the change in the above four signals is determined by the determiner 10,
If any of the signals exceeds a certain standard, it can be detected as a moving object crossing or approaching. As a result, the detection probability is significantly improved.

FIG. 10 shows a partially modified embodiment of the embodiment shown in FIG. In this embodiment, the amplitude meter 22 on the far end side of the detector shown in FIG. 8, between the phase meter 23 and the determiner 10, and the amplitude meter 25 on the near end side,
A square phase adder 2 is provided between the phase meter 26 and the determiner 10, respectively.
The only difference is that 7.28 was inserted.

The square phase adder 27 calculates the reference amplitude ■ from the output of the amplitude meter 22.
The square of the signal obtained by subtracting c1 and the phase meter 23
The signal (voltage value) obtained by subtracting the reference phase φ from the output of
The square-phase adder 2 is configured to output a signal obtained by adding the square root of
8 is the sum of the square of the signal obtained by subtracting the reference amplitude ■c2 from the output of the amplitude e+ 25, and the square of the signal (voltage value) obtained by subtracting the reference phase φ2 from the output of the phase meter 26. It is configured to output a signal obtained by taking the square root.

In this embodiment configured as described above, when a person walks in the middle of two open coaxial cables from Z-0 toward Z-ρ, the output signal of the far-end coupled reception square-phase adder 27 is as shown in FIG. 11(a), and the output signal of the square-phase adder 28 for near-end coupling reception is as shown in FIG. 11(b). In reality, the outputs of these two square-phase adders partially decrease in level as explained in FIG. 5, but by combining both signals, it is possible to
Approach can be detected with constant high sensitivity, increasing detection probability.

In addition, in any of the above embodiments, the moving object 5 such as a person or a car
The explanation has been given using an example of detecting when a moving object 5 crosses the detection lines of two open coaxial cables 1.2, but it is clear that the same detection function will occur even if a moving object 5 approaches the two detection lines. Will.

[Effects] As explained in detail above, in the present invention, receivers for the near-end coupled signal and the far-end coupled signal are provided at both ends of the open coaxial cable on the receiving side, and the output signals of these receivers are detected by the discriminator. The transversal movement or approach of the moving object is detected based on whether the amplitude of the received signal, the amplitude and phase, or the squared phase addition output of the amplitude and phase is within a predetermined range with respect to the reference value. As a result, the detection sensitivity does not decrease in the length direction of the detector, and the influence of dead points can be removed at any position shifted in the length direction, so that the detector can be used for practical use with stable sensitivity. Obtainable.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a first embodiment of the crossing/approach detector according to the present invention, FIG. 2 is a diagram of an example of the configuration of an open coaxial cable, FIG. 3 is an explanatory diagram of the operation, and FIG. A schematic diagram of the second embodiment, FIG. 5 is an explanatory diagram of the action, and FIG. 6 is the fourth embodiment.
A schematic block diagram of a partially modified actual flow side of the embodiment shown in the figure, Fig. 7 is an explanatory diagram of the operation, Fig. 8 is a schematic block diagram of the third embodiment, Fig. 9 is an explanatory diagram of the operation, and Fig. 10 is a schematic block diagram of a partially modified embodiment of the embodiment shown in FIG. 8; FIG. 11 is an explanatory diagram of the operation; FIG. 12 is a schematic configuration diagram of a conventional detector;
The figure is a schematic block diagram of the first experiment, FIGS. 14 and 15 are explanatory diagrams of the action, FIG. 16 is a schematic block diagram of the second experimental example, and FIG. 17 is an explanatory diagram of the action. 1.2...Open type coaxial cable, 3...
・Transmitter, 4.9...Receiver, 5...
...Moving object, 6.7.8...Reflection-free terminator, 10.10',
10″・・・Judgment device, 11.12.15.16・
...... Turnout, 13.17... Attenuator, 1
4.18... Phase shifter, 21.24...
Distributor, 22.25... Amplitude needle, 23.26.
... Phase meter, 27.28 ... Square phase adder. Akira tsuse I (sanguisho gkurono ■ Akira!!! lI 謂 (plastic sleep 11) Q ■ =667- (Sōnebori<D) , O-note 4 tsol ['e ″′ (■Sleeping♀〈I〈I〈)

Claims (5)

[Claims] (1) A transmitter is connected to one end of one of two open coaxial cables with different phase constants that are provided in parallel and separated by a predetermined distance from each other, and a non-reflection terminator is connected to the other end of the cable.
A receiver for receiving the far-end coupled signal is connected to the far end of the other cable on the side farther from the transmitter, and a receiver for receiving the near-end coupled signal is connected to the near end of the other cable on the side closer to the transmitter. The receiver for receiving the end coupled signal and the receiver for receiving the near end coupled signal are provided with a determiner for determining whether the amplitude of any of the signals is within a predetermined range with respect to a reference value, and A crossing/approaching detector, characterized in that the crossing/approaching detector detects the crossing movement or approach of a moving object by detecting an amplitude change of a far-end coupling signal or a near-end coupling signal using a determiner. (2) A circuit is provided in the receiver for far-end coupled reception, which guides a signal from the transmitter through one of the cables and uses this signal to cancel the far-end coupled signals of the two open coaxial cables; The receiver for near-end coupled reception is equipped with a circuit that directly guides the signal from the transmitter and uses this signal to cancel the near-end coupled signals of the two open coaxial cables to determine the far-end coupled reception level and the near-end signal. Set the combined signal level to 0.
The crossing/approaching detector according to claim 1, wherein the crossing/approaching detector detects the crossing movement or approach of the moving object by detecting an amplitude change of far-end coupling or near-end coupling by the determiner. . (3) A unidirectional element is connected to both ends of the other open coaxial cable.
Crossing/approach detector described in . (4) The receiver for receiving the far-end coupled signal and the near-end coupled signal includes an amplitude meter that receives an amplitude component and a phase meter that receives a phase component, and the determiner is configured to determine the amplitude of the far-end coupled signal, It consists of a determiner that determines whether the phase, the amplitude of the near-end coupled signal, or the phase is within a predetermined range with respect to a reference value. The crossing/approaching detector according to claim 1, wherein the crossing/approaching detector detects movement or approaching. (5) A sum-of-squares adder for combining the outputs of the amplitude meters and phase meters of the far-end coupled signal and near-end coupled signal receivers is provided between the amplitude meters and phase meters of the respective receivers and the determining device. , wherein the determiner determines whether any of the output signals of the sum-of-squares adder is within a predetermined range with respect to a reference value; 5. The crossing/approaching detector according to claim 4, wherein the crossing/approaching detector detects crossing movement or approaching.