JPH09159715A - Current route searching method of wiring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the searching of the current route of wiring without necessitating a lead wire for sending a reference signal, and reduce the time for searching the current route. SOLUTION: In this method, a signal from a signal generator 1 is applied to wiring, the applied signal is detected by a lock-in amplifier 12, and the flowing path of the applied signal is pursued, thereby searching the current route of wiring. In this case, the signal generator 1 turns on and off (ON.OFF) a sinusoidal wave of a frequency f1Hz and a sinusoidal wave of a frequency nf1Hz (n>8) at intervals of 1/(2f1) sec, synchronizing with the signal of f1Hz, and the two burst signals are added together. From one side of the wiring, the added signal is applied, and the current is received on the wiring route. A reference signal of f1Hz is formed on the basis of the signal component of nf1Hz. By using the reference signal, the sinusoidal wave of f1Hz in the current is detected by the lock-in amplifier 12, and the current value and the phase difference of the detected sinusoidal wave of f1Hz are measured, thereby detecting the flowing direction of the signal current applied to the wiring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a weak signal current to a wiring, measures the current value and phase of the signal current on the route where the signal current of the wiring flows, and determines the direction in which the signal current flows at each measurement location. By knowing whether the termination condition of the wiring route through which the signal current flows is a capacitance component, an inductance component or a resistance component, the target ground wire, communication cable,
The present invention relates to a wiring current route search method capable of investigating a wiring route and a connection state of a power cable or the like.

[0002]

2. Description of the Related Art FIG. 10 is a diagram for explaining a conventional method of applying a current route search signal to a ground line in a building from a signal generator to perform a current route search of the ground line. A conventional ground line current route search method is as shown in FIG.
A method has been used in which the current from the signal generator 1 is measured by a signal receiver 7 such as a spectrum analyzer or a level measuring device, and the route of the current is followed.

A lock-in amplifier using a signal from a signal generator as a reference signal is used to eliminate the influence of a noise current flowing through a ground line and to measure the magnitude and phase of a minute signal current. There is.

[0004]

SUMMARY OF THE INVENTION The present inventor has found the following problems as a result of studying the above conventional technology.

In the former method, the magnitude of the signal current is known, but the direction is unknown, and if the signal current is reduced in order not to affect the equipment connected to the ground line, the signal current is grounded. Since the search becomes impossible due to the noise current flowing in the line, there is a problem that the route search of the ground line cannot be performed accurately.

Further, in the latter method, it is necessary to transmit the reference signal from the signal generator to the lock-in amplifier by using the metallic cable or the radio wave. There was a problem of this. For example, it was necessary to connect a signal generator for inputting a signal to a wiring and another metallic cable for sending a reference signal between a lock-in amplifier for measuring a current value and a phase. In addition, when performing such a measurement on each floor in the building, it is necessary to connect a cable or the like for transmitting a reference signal to the measurement location on the floor where the measurement is performed each time. Also,
When the measurement place moves to various floors or places, the line for transmitting this reference signal needs to be long, and it has to be moved at each measurement, which requires a lot of labor and time. There was a problem.

Further, in the method using wireless, there is a possibility that the wireless radio waves may affect electronic devices in the vicinity, and the radio waves may not reach due to walls or the like. That is, there is a problem that even a wireless signal may not be implemented due to influence on the surroundings, propagation loss, and the like.

In the spectrum analyzer and level measuring device, the phase difference between the applied current and the received signal cannot be measured, and it is difficult to specify the wiring direction.

Further, in the method using the lock-in amplifier, it is necessary to wire the conducting wire for transmitting the reference signal, so that there is a problem that workability is poor in measurement in a large building.

On the other hand, the center frequency f2 hertz (H
Workability is improved by sending the reference signal using the burst signal or the sinusoidal amplitude modulation signal of z), but in a noisy building, the noise may affect the measurement.

In order to solve this, the center frequency f2 Hz
In order to detect the burst signal or the sine wave amplitude modulation signal of the noise from the noise with high accuracy, it may be possible to pass through the band pass filter having the center frequency f2 Hz. However, when the pass band width of the filter is wide, the noise is sufficient. There is a problem that the removal effect cannot be obtained.

In order to reduce noise, the pass band width of the filter is narrowed to (f2 + f1) Hz and (f2-f).
1) When the frequency component of the sideband of Hz is suppressed, the degree of modulation of the filter output decreases, and if the pass band width is further reduced, the filter output becomes a sine wave with a constant amplitude, and a burst or sine wave modulation signal is generated. There was a problem that the reference signal could not be detected.

An object of the present invention is to provide a technique capable of searching a current route of a wiring without requiring a conductor for transmitting a reference signal.

Another object of the present invention is to provide a technique capable of shortening the current route search work time.

Another object of the present invention is to provide a technique capable of reducing the influence of noise current flowing through wiring to the utmost limit.

Another object of the present invention is to provide a technique capable of accurately measuring even in a noisy building.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0018]

The outline of a typical invention among the inventions disclosed in the present application will be briefly described as follows.

(1) Wiring the signal from the signal generator (ground wire or communication cable, power cable, etc.)
In the method for searching a current route of a wiring, the signal is applied to the sine wave, the lock-in amplifier detects the applied signal, and the path of the applied signal is traced, and a sine wave having a frequency f1 Hz and a frequency nf1 Hz (n> 8) ) 1 /
Wiring is performed by adding two signals of burst waves that are turned on / off in synchronization with the signal of the frequency f1 Hz at intervals of (2f1) seconds, and apply the added signal from one of the wirings. A current is received on the route, a reference signal of frequency f1 Hz is created from the received signal on the wiring route, and a sine wave of frequency f1 Hz in the current is detected by the lock-in amplifier by the reference signal,
This is a method for searching a current route of a wiring, which measures a current value and a phase difference of a detected sine wave of a frequency f1 Hz and detects a flowing direction of a signal current applied to the wiring.

(2) In the wiring current route searching method of (1), the signal applied from one of the wirings is obtained by modulating a sine wave of the frequency nf1 Hz by an amplitude modulation or another modulation method at a frequency of f1 Hz. The modulated signal received on the wiring route is detected to generate a reference signal of f1 Hz.

(3) In the method for searching the current route of the wiring of (1) or (2), a reference signal of frequency f1 Hz is generated from the received signal on the wiring route with reference to the signal component of frequency nf1 Hz. is there.

(4) In the method for searching a current route for a wiring according to (1) or (2), the received signals on the wiring route are centered at frequencies f2 (= nf1) Hz and (f2-f1).
A reference signal is generated by distributing the outputs of these filters to a narrow band filter of Hz and detecting the signals obtained.

(5) In the method for searching the current route of the wiring of (1) or (2), the received signal on the wiring route has a center frequency f2 (= nf1) Hz and a frequency (f2 +).
f1) It is distributed to a narrow band filter of Hz, the signals obtained by synthesizing the outputs of these filters are detected, and a reference signal is created.

(6) In the wiring current route searching method of (1) or (2), the received signal on the wiring route has a center frequency f2 (= nf1) Hz and a frequency (f2-f).
1) It is distributed to narrow band filters of Hz and (f2 + f1) Hz and the signals obtained by synthesizing the outputs of these filters are detected to create a reference signal.

That is, the outline of the present invention is a method of detecting a reference signal by flowing it through a ground line at a carrier frequency of f2 Hz. Further, in order to accurately extract the reference signal from noise, the center frequency f2 Hz and frequency ( f2 + f1) Hz or (f2-f1) Hz narrow band filters are distributed and the outputs of these filters are added to obtain a signal in which the carrier of frequency f2 Hz is amplitude-modulated at frequency f1 Hz, and this is detected. Is used to obtain a reference signal of frequency f1 Hz.

According to the above-mentioned means, the sine wave having the frequency f1 Hz and the sine wave having the frequency nf1 Hz which is n times the frequency f1 are turned on / off (ON) at intervals of 1 / (2f1) seconds as signals from the signal generator. The two signals of the turned off waveform are added and applied to the search target wiring (cable), and first, the frequency f1 Hz reference signal is created from the amplitude of the component of the frequency nf1 Hz. Next, this reference signal is put into a lock-in amplifier as a reference signal, and the frequency f
The current value and phase of the 1 Hz component are detected.

Also, turn on the sine wave of frequency nf1 Hz.
Instead of turning it off (ON / OFF), frequency nf1H
The sine wave of z is modulated at a frequency f1 Hz by amplitude modulation or another modulation method, and this is detected on the receiving side to obtain a frequency f1H.
A reference signal of z is created, and a sine wave having a frequency f1 Hz in the signal current is detected by the lock-in amplifier using this as a reference signal. In other words, the added signal of the measurement signal and the reference signal input to the wiring is separated at the measurement location, and the separated reference signal is used as the reference of the lock-in amplifier to synchronously detect the measurement signal and measure it. Even if the measurement location is far away, the current value and phase can be measured easily and accurately without connecting with a conductor such as a cable for transmitting a reference signal or using radio waves.

For example, a method of separating a combined signal of a measurement signal and a reference signal input to a ground line or the like at a measurement location, and using the separated reference signal as a reference of a lock-in amplifier to perform synchronous detection of the measurement signal to perform measurement. In the above, it is possible to effectively suppress the influence of the noise current flowing in the ground line, and it is possible to search for a route such as the ground line by injecting a low level current into the ground line even in a poor electromagnetic environment.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings together with its embodiments (examples).

In all the drawings for explaining the embodiments (examples), those having the same function are designated by the same reference numeral, and the repeated description thereof will be omitted.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
This is (Example 1), and the applicant previously filed Japanese Patent Application No. 7
FIG. 3 is a circuit configuration diagram for explaining a current route search method in which a reference signal of −258534 is directly input from a signal generator to a lock-in amplifier by a metal cable, 1 is a signal generator, 2 is a ground wire or a communication cable, and a power supply. Cables such as cables, 3 are ground wire electrodes, 4 are earth return paths,
8 is a secondary side ground electrode of the low voltage distribution system, 9 is a distribution transformer, 10 is a power outlet, 11, 11 'and 11 "are current probes, 12 is a lock-in amplifier, 13 is an oscilloscope, 14 is a divider (signal (Distributor), 15 is a reference signal line, 16 is a capacitor, and G is a ground side terminal of the signal generator 1.

In the first embodiment, as shown in FIG. 1, a signal generator 1 sends a signal of 1 kilohertz (kHz) to a circuit and a reference signal is sent to a reference signal line 1.
5 is connected so as to be sent to the lock-in amplifier 12.

As shown in FIG. 1, the ground line current route searching method according to the first embodiment is such that, as shown in FIG. 1, one terminal of the signal generator 1 and a conductor of a ground side electrode of a power outlet are coupled by a capacitor 16 to generate a signal. A loop circuit is formed from the device 1 to the ground wire 2, the ground wire electrode 3, the earth return path 4, the secondary side ground electrode 8 of the low voltage distribution system, the power outlet 10 and the capacitor 16.

The signal current of the signal generator 1 is applied to the ground line 2 for searching the current route, and the signal current is distributed by the divider 14 and transmitted to the lock-in amplifier 12 using the reference signal line 15. The signal current flowing through the ground line 2 is measured by the current probe 11, the lock-in amplifier 12, and the oscilloscope 13 in a non-contact state, the one with a large signal current is searched for, and the current direction is detected. , 11 ", the current route of the target ground line (wiring) can be searched by simultaneously or sequentially measuring along the assumed route.

However, the method according to the first embodiment requires a conductor for transmitting a reference signal, which is inconvenient to handle in a large-scale building.

It is possible to omit the capacitor 16 and directly apply it, but it is necessary to confirm before connection that no voltage is present on the connecting line.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
Circuit configuration diagram for explaining the current route search method that applies the added signal of the measurement signal and the reference signal to the wiring, separates the added signal at the measurement location, and uses the separated reference signal as the reference signal of the lock-in amplifier , G1 is the oscillator of the measurement signal of frequency f1 Hz, G2 is the frequency of nf1 Hz
ON / OFF at intervals of 1 / (2f1) seconds
F) an oscillator for generating the waveform, 20 a measuring unit, 21 a filter, 22 a reference signal generator, and 23 a lock-in amplifier.

In the current route search method of the second embodiment, as shown in FIG. 2, signals of the oscillator G1 and the oscillator G2 are added and applied to the wiring. Next, the measurement unit 20 passes the current from the current probe 11 for detecting the current flowing through the cable wiring through the filter 21 tuned to the frequency nf1 Hz,
This is input to a reference signal generator 22 for detecting and generating a reference signal. A reference signal of frequency f1 Hz is supplied from the reference signal generator 22 to the lock-in amplifier 23,
By synchronously detecting with the frequency f1 Hz as a reference, the current value and phase of the component of the frequency f1 Hz in the current from the current probe 11 are measured.

FIG. 3A shows 1 kHz from the oscillator G1.
, (B) is a signal of 20 kHz signal from the oscillator G2 turned on and off (ON / OFF) in 0.0005 seconds, and (c) is a signal obtained by adding signals from the oscillators G1 and G2. Apply to the cable. The measurement principle based on the current waveform when this signal is sent to the wiring route is shown below.

FIG. 4 shows an equivalent circuit side of the wiring of the embodiment (Example 2) of the present invention, and is a diagram for explaining a case where the current applied from the signal generator 1 is measured by the probes 1, 2, and 3. Is. Opening the load (Z) 17 and setting it to 2.2 μF 2
The measurement was performed under two conditions. The arrows attached to the probes 1, 2, and 3 indicate the polarities of the probes.

FIG. 5 shows that when the load (Z) 17 is opened,
It can be seen that the probe 1 and the probe 2 have the same waveform, and all the current from the signal generator 1 flows in the direction of the probe 2. It can be confirmed that the phase of the signal of 1 kHz is not deviated with reference to the burst signal of 20 kHz.

FIG. 6 shows current waveforms of the probe 1 and the probe 2 when the load (Z) 17 is set to 2.2 μF. From this, from the time between the beginning of the burst signal of 20 kHz and the peak of the 1 kHz signal in the waveform of the probe 1,
When the phase of kHz is obtained, the probe 1 has 360 μs = 1.
30 ° (degrees), with probe 2 430 μs = 155 °
It can be seen that the phase of the probe 2 lags the phase of the probe 1 by 25 ° (degrees).

In the same circuit to be measured, when the reference signal is directly input from the signal generator 1 to the lock-in amplifier 12 with a metal cable, the measured value is 21 ° (degrees).
It was confirmed that there was a delay and almost the same measurement values were obtained.

Further, the signal of 1 kHz from the oscillator G1 and the signal of 20 kHz from the oscillator G2 are 0.0005.
Instead of adding signals that are turned on and off at intervals of 2 seconds, a sine wave of 20 kHz is generated from the oscillator G2 at 1 k
A signal amplitude-modulated with a measurement signal of Hz is generated and applied to the wiring in the same manner as in the case of adding the above-mentioned signals.
The same measurement can be performed by extracting a 1 kHz sine wave reference signal from the kHz signal and inputting it to the lock-in amplifier 12.

As can be seen from the above description, according to the second embodiment, the signal from the signal generator 1 is f1H.
The sine wave of z and the sine wave of nf1 Hz having a frequency n times f1 are turned on / off (ON / OF) at intervals of 1 / (2f1) seconds.
The signal obtained by adding the two waveforms F) is applied to the search target wiring, and first, the frequency f1 is calculated from the amplitude of the component of nf1 Hz.
Create a Hz reference signal. Next, this reference signal is input to the lock-in amplifier 12 as a reference signal, and the lock-in amplifier 12 detects the current value and phase of the f1 component.

Further, a sine wave having a frequency of nf1 Hz is turned on.
Instead of turning it off (ON / OFF), frequency nf1H
The sine wave of z is modulated at a frequency f1 Hz by amplitude modulation or another modulation method, and this is detected on the receiving side to obtain a frequency f1H.
A z reference signal is generated, and the lock-in amplifier 12 detects a sine wave having a frequency f1 Hz in the signal current by using this as a reference signal. In other words, the added signal of the measurement signal and the reference signal input to the wiring is separated at the measurement location, the separated reference signal is used as the reference of the lock-in amplifier 12, and the measurement signal is synchronously detected to measure the signal input. Even if the point and the measurement location are distant from each other, the current value and the phase can be easily and accurately measured without connecting with a conducting wire such as a cable for transmitting a reference signal or using a radio wave.

(Third Embodiment) FIG. 7 shows a third embodiment of the present invention.
3 is a block diagram showing a schematic configuration of a measuring unit in FIG.
0 is the measuring unit in the third embodiment, 31 is the center frequency f2
First narrowband bandpass filter, 32 is a second narrowband bandpass filter having a center frequency (f2 + f1), 33
Is an adder, and 34 is an envelope detector.

In the measuring section 30 of the third embodiment, the voltage from the current probe 11 for detecting the current flowing through the cable is tuned to the first frequency f2 (= nf1) Hz.
Narrow band bandpass filter 31 and center frequency (f2 + f
1) Second narrow band bandpass filter 32 tuned to Hz
Distribute to The outputs of these two filters are added to the adder 3
When the output A is added by 3, and envelope detection is performed by the envelope detector 34, a signal of frequency f1 Hz is obtained. This signal is input to the lock-in amplifier 21 as the reference signal B, and is synchronously detected with the reference signal B to inject the signal from the signal generator 1 (FIG. 2) into the ground line 2 (FIG. 2) and the like, which is a search signal of frequency f1 Hz. Detect the amplitude and phase difference of.

FIG. 8 (a) shows the signal current waveform applied from the signal generator 1 to the ground line 2, and FIG. 8 (b) shows the measured waveform of the output A of the adder 33 of FIG. 7 with the center frequency f2 Hz. First
Narrow band bandpass filter 31 and (f2 + f1) Hz
The signal after passing through the second narrowband bandpass filter 32 of No. 1 is added. 8C shows a waveform obtained by performing envelope detection on the waveform of FIG. 8B. By using this waveform as the reference signal B of the lock-in amplifier 21, the signal current shown in FIG. Frequency f1H
The signal amplitude and phase of z can be measured.

FIG. 9A shows the spectrum of the signal current applied from the signal generator 1 to the ground line 2. Thus, the spectrum of the search signal is at the frequency f1 Hz and the frequency f2
A signal in which Hz is turned on / off is composed of a carrier having a center frequency of f2 Hz and sidebands on both sides of the carrier.

Here, when the band of the filter is narrowed at the center frequency f2 Hz in order to reduce the influence of noise as in the case of the filter A in FIG. 9B, the modulation signal component which is modulated in a burst form. Is blocked, the signal after passing through the filter becomes a signal having a constant amplitude with a center frequency f2 Hz, and the reference signal B cannot be taken out. On the contrary, when a filter having a wide bandwidth such as the filter B is used to extract the reference component, the center frequency f
Since the noise component between 2 Hz and f2 + f1 Hz also passes, the influence of noise becomes large.

On the other hand, in the method of the third embodiment,
Carrier frequency of center frequency f2Hz and (f2 + f1) Hz
It is possible to extract the sideband component of each using the narrow band filter A and the filter C and add them to obtain the reference signal component, and it is possible to minimize the influence of noise.

When the sine wave having the center frequency f2 Hz is amplitude-modulated in the same phase as the search signal having the frequency f1 Hz and applied to the ground line 2, the spectrum of the modulated signal has the center frequency f2 Hz, frequencies f2 + f1 Hz and f2-f1H.
Three types of frequency components of z are included, and it is possible to obtain a reference signal of frequency f1 Hz by extracting at least two types of these. Therefore,
A narrow band filter is similarly used to reduce the influence of noise.

As described above, the invention made by the present inventor is:
Although specifically described based on the embodiment (example),
The present invention is not limited to the above-described embodiment (example), and it is needless to say that various changes can be made without departing from the gist of the present invention.

[0055]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) Since the reference signal of the lock-in amplifier is created at the measurement point by using the combined signal of the measurement signal and the reference signal as the signal from the signal generator, the wiring without the need for a conductor for transmitting the reference signal is required. You can search the route.

(2) Due to the above (1), the current route search work time can be shortened.

(3) The influence of the noise current flowing through the wiring can be reduced to the utmost limit.

(4) Accurate measurement can be performed even in a noisy building.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram for explaining a current route search method for directly inputting a reference signal to a lock-in amplifier according to a first embodiment of the present invention.

FIG. 2 is a current route in which a sum signal of a measurement signal and a reference signal according to the second embodiment of the present invention is applied to a wiring, the sum signal is separated at a measurement location, and the separated reference signal is used as a reference signal of a lock-in amplifier. It is a circuit block diagram for explaining a search method.

FIG. 3 is a diagram for explaining addition of a measurement signal and a reference signal according to the second embodiment.

FIG. 4 is a diagram showing an equivalent circuit of the wiring of the second embodiment, and is a diagram for explaining a case where a current applied from a signal generator is measured by the probes 1, 2, and 3.

FIG. 5 is a diagram for explaining a measurement result of the second embodiment.

FIG. 6 is a diagram for explaining a measurement result of the second embodiment.

FIG. 7 is a block diagram showing a schematic configuration of a measuring unit according to a third embodiment of the present invention.

FIG. 8 is a signal waveform diagram of each part in the third embodiment.

FIG. 9 is a diagram for explaining the operation and effect of the third embodiment.

FIG. 10 is a diagram for explaining a conventional route search method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Signal generator, 2 ... Ground wire, 3 ... Ground wire electrode, 4 ... Ground return path, 5 ... Current return ground electrode, 6 ... Return lead wire, 7 ... Signal receiver, 8 ... 2 of low voltage distribution system Secondary side ground electrode, 9 ... Distribution transformer, 10 ... Power outlet, 11,
11 ', 11 "... Current probe, 12 ... Lock-in amplifier, 13 ... Oscilloscope, 14 ... Divider (signal distributor), 15 ... Reference signal line, 16 ... Capacitor,
17 ... Load (Z), 20 ... Measuring unit, 21 ... Filter, 2
2 ... Reference signal generator, 23 ... Lock-in amplifier, G ... Ground side terminal of signal generator 1, G1, G2 ... Oscillator, 30 ...
Measuring unit, 31 ... First narrow band bandpass filter, 32 ...
Second narrow band bandpass filter, 33 ... Adder, 34 ...
Envelope detector.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shoichi Kuramoto 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (6)

[Claims] 1. A signal from a signal generator is applied to a wiring (a ground wire or a cable such as a communication cable or a power cable), and the applied signal is detected by a lock-in amplifier,
In the method for searching a current route of a wiring for tracing a route of the applied signal, a signal generator generates a frequency f1 hertz (H
2) a burst wave in which a sine wave of z) and a sine wave of frequency nf1 Hz (n> 8) are turned on / off (ON / OFF) in synchronization with the signal of the frequency f1 Hz at 1 / (2f1) second intervals. Two signals are added, the added signal is applied from one of the wirings to receive a current on the wiring route, a reference signal having a frequency f1Hz is generated from the received signal on the wiring route, and the current is generated by the reference signal. Wiring characterized by detecting the sine wave of the frequency f1Hz in the inside with a lock-in amplifier, measuring the current value and phase difference of the detected sine wave of the frequency f1Hz, and detecting the flowing direction of the signal current applied to the wiring Current route search method. 2. The signal applied from one of the wirings is a sine wave having a frequency of nf1Hz, which is amplitude-modulated or another modulation method at a frequency of f1Hz, and the modulated signal received on the wiring route is detected. 2. A reference signal having a frequency f1 Hz is produced by the above method.
A method for searching a current route for wiring described in. 3. The wiring current route searching method according to claim 1, wherein a reference signal of frequency f1 Hz is generated from the received signal on the wiring route with reference to the signal component of frequency nf1 Hz. . 4. The received signal on the wiring route is distributed to narrow band filters having center frequencies f2 (= nf1) Hz and (f2-f1) Hz, and signals obtained by synthesizing outputs of these filters are obtained. The current route searching method for wiring according to claim 1 or 2, wherein the reference signal is detected to generate a reference signal. 5. The received signal on the wiring route is distributed to narrow band filters having center frequencies f2 (= nf1) Hz and (f2 + f1) Hz, and the signals obtained by synthesizing the outputs of these filters are detected. The method for searching a current route of a wiring according to claim 1 or 2, wherein the reference signal is generated by the above method. 6. The received signal on the wiring route is distributed to narrow band filters having a center frequency f2 (= nf1) Hz, frequencies (f2-f1) Hz and (f2 + f1) Hz, and outputs of these filters are combined. The signal obtained by the above is detected to produce a reference signal.
Alternatively, the method for searching the current route of the wiring described in 2.