JPH05336112A - Noise detector for isdn line - Google Patents

Abstract

PURPOSE:To simply detect the occurrence of noise on a signal line for each kind of noise and to improve a noise evaluation job and a noise production prevention job by providing plural noise detection circuits detecting individually various kinds of noise caused on the signal line. CONSTITUTION:A noise detector 10 integrated in a diagnosis equipment 8 is connected to a signal line R3a and a T line 3b. The noise detector 10 is made up of a common mode noise detection section 11 detecting a common mode noise inputted externally from a power supply or an antenna or the like caused on a signal line 3, a normal mode noise detection section 12 detecting a normal mode noise caused between signal lines 3, a display section 13 displaying the result of detection of each of the noise detection sections 11,12 and a clock circuit 18 counting a current time. Then the result of detection of each of the detection sections 11,12 is displayed on the display section 13 and sent to a main control section 14 comprising a computer controlling the entire diagnostic device 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ISDN, and more particularly to an ISDN line noise detecting apparatus for properly detecting noise generated on each signal line of ISDN, including the type of noise.

[0002]

2. Description of the Related Art ISDN (Integrated Services Digital Network) is adopted as a communication system for transmitting a large number and multiple digital data at high speed and efficiently. This ISD
In N, an ISDN exchange installed in the office of the telephone company, for example, D installed in the company via a data line.
A large number of terminals such as a telephone, a telex, a personal computer, and a facsimile are connected to the SU (line terminating device), and the DSU (line terminating device) is connected.

The interface between the DSU (circuit terminating equipment) and each terminal is composed of a [2B + D] basic interface. The signal line that connects the DSU and each terminal is roughly divided into DSU (line terminator)
From each terminal to the R line that transmits signals from each terminal to each terminal
It is composed of a T line that transmits a signal to the SU. Signals transmitted on the R and T lines are generally AMI (Alternat).
e Mark Inversion) Encoded digital pulse signal. The R line and the T line are each composed of a pair of signal lines.

In general, a signal transmitted on a signal line wired in a building has a power source noise of 50 Hz or 60 Hz, and a high frequency EM output from various electronic devices installed in the vicinity.
I noise and noise due to radio waves radiated from an antenna of an external wireless device are superimposed. Such a power supply,
The noise input from the ground and antenna to the signal line is called common mode noise.

On the other hand, the noise generated between the signal lines in the R line or the T line of the signal line is called normal mode noise. This noise has a waveform and a frequency approximate to the signal waveform of the pulse signal to be transmitted. Have.

Therefore, when a new ISDN is constructed, it is necessary to check whether the above-mentioned common mode noise or normal mode noise is superimposed on the pulse signal transmitted on each signal line. Then, when the noise more than the allowable value is generated, it is necessary to take various noise prevention measures.

[0007]

However, conventionally, there is a test apparatus that can easily detect the type of noise described above and the type of noise that has been generated in this signal line. There wasn't. Therefore, in order to detect the noise component superimposed on the signal transmitted on the signal line,
By connecting an oscilloscope or logic analyzer to the signal line, an operator observes the waveform of the pulse signal transmitted through each signal line, and if noise is superimposed, or if noise is superimposed, the noise I was observing what kind it was.

Therefore, much labor and cost are required. Further, in order to find the normal mode noise generated between the signal lines from the pulse signal waveform displayed on the oscilloscope and to specify the noise type, it is necessary to have a high level of knowledge about ISDN and a skilled technique for measurement. ..

The present invention has been made in view of the above circumstances, and noise is generated in a signal line by providing a plurality of noise detection circuits that individually detect each type of noise generated in the signal line. It is an object of the present invention to provide an ISDN line noise detection device capable of easily detecting the above-mentioned noises for each noise type and significantly improving the work efficiency of the noise evaluation work and the noise generation prevention work that follows.

[0010]

In order to solve the above problems, an ISDN line noise detecting apparatus according to the present invention is provided with an ISDN.
A common mode noise detection unit that detects common mode noise that is input from the outside such as a power supply or an antenna that occurs in the signal line, and a normal mode noise detection unit that detects normal mode noise generated between the signal lines in the signal line, And a display unit that displays the detection result of each noise detection unit.

Then, the common mode noise detector extracts a high frequency noise component contained in the signal transmitted on the signal line with a high pass filter, and a high frequency noise component of a predetermined level or more is extracted from the extracted high frequency noise component. A high-frequency EMI detection circuit that outputs a high-frequency noise detection signal when present, and a high-pass filter to extract the high-frequency signal component contained in the signal transmitted on the signal line, and a counter to measure the extraction interval of the high-frequency signal component The pulse noise detection circuit outputs a pulse noise detection signal when the measured value is a time interval determined by the type of noise.

Further, the normal mode noise detector measures the signal level of the AMI-coded pulse signal transmitted on the signal line, and outputs a noise pulse detection signal when the measured value is outside the allowable level range. It is composed of an abnormal signal level detection circuit and an abnormal pulse width detection circuit which measures the pulse width of the pulse signal and outputs a noise pulse detection signal when the measured value is outside the allowable pulse width range.

[0013]

In the ISDN line noise detecting device thus constructed, when high frequency noise is generated in the signal line due to, for example, radio waves radiated from the antenna, the high frequency noise is generated by the high pass filter. To be extracted. If the noise signal level is equal to or higher than a predetermined level, the high frequency EMI detection circuit outputs a high frequency noise detection signal.

Further, for example, when power source noise of 50 Hz or 60 Hz occurs, this power source noise component is extracted by the high-pass filter, and when the extraction interval becomes a time interval corresponding to 50 Hz or 60 Hz, a pulse noise detection signal is output. It

The above is the operation when common mode noise is generated. Next, the operation when normal mode noise occurs will be described.

The signal level and pulse width of each pulse waveform of the AMI-encoded pulse signal transmitted on the signal line are constantly measured by the abnormal signal level detection circuit and the abnormal pulse width detection circuit. Therefore, when a noise pulse whose signal level is outside the allowable level range is input, it is detected by the abnormal signal level detection circuit. When a noise pulse whose pulse width is out of the allowable pulse width range is input, it is detected by the abnormal pulse width detection circuit.

As described above, the noise occurrence can be detected, and the typical noise type is automatically specified.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram showing the entire ISDN in which the noise detecting device of the embodiment is incorporated. For example, a plurality of DSUs (line terminators) 2 are connected to an ISDN exchange 1 installed in a telephone office of a telephone company via a data line. A large number of terminals 4 are connected to each DSU 2 via a signal line 3. Information is exchanged between the DSU 2 and each terminal 4 based on the basic interface of the [2B + D] configuration described above.

The ISDN exchange 1 has a digital DSU 2
In addition to the above, an existing analog line 5 and a center unit 7 including a computer for monitoring and controlling the operation of the ISDN as a whole are connected via a dedicated DSU 6.

Then, the diagnostic device 8 incorporating the noise detecting device of the embodiment of the present invention is connected to the signal line 3 to be tested as required. The diagnostic device 8 is also connected to the ISDN exchange 1 via a dedicated DSU 9.
Therefore. The diagnostic result of the diagnostic device 8 can be directly transmitted to the center device 7 via the ISDN exchange 1 without passing through the signal line 3 to be tested. On the contrary, it is also possible to directly remotely operate the diagnostic device 8 from the center device 7.

The signal line 3 connecting the DSU 2 and each terminal 4 is, as shown in FIG. 3, an R line 3a consisting of a pair of signal lines for transmitting a signal from the DSU 2 to each terminal 4, and each terminal 4 To the DSU 2 and a T line 3b composed of a pair of signal lines.

The noise detecting device 10 incorporated in the diagnostic device 8 is connected to the R line 3a and the T line 3b of the signal line 3. The noise detection device 10 detects a common mode noise detection unit 11 that detects common mode noise that is input to the signal line 3 from the outside, such as a power source or an antenna, and normal mode noise that occurs between signal lines in the signal line 3. Normal mode noise detector 12 and each noise detector 1
The display unit 13 displays the detection results of Nos. 1 and 12, and the clock circuit 18 that measures the current time. And
The detection results of the detection units 11 and 12 are displayed on the display unit 13 and transmitted to the main control unit 14 including a computer that controls the entire diagnostic device 8.

FIG. 1 is a block diagram showing a schematic configuration of a common mode noise detector 11 for detecting common mode noise on the T line 3b.

The common mode noise detection section 11 is roughly divided into a pseudo communication circuit 15 for impedance matching shown in FIG. 5, which is assumed to be a terminal connected between a pair of signal lines forming a T line 3b, and a pseudo communication circuit 15 for impedance matching. A high frequency EMI detection circuit 16 for detecting high frequency noise appearing between both terminals of the resistor 15a of the pseudo communication circuit 15, and a pulse noise detection circuit for detecting pulse noise appearing between both terminals of the resistor 15a of the pseudo communication circuit 15. It is composed of 17 and.

T input into the high frequency EMI detection circuit 16
The AMI-coded pulse signal transmitted on the line 3b is attenuated by the attenuator 16a at a predetermined attenuation rate and then input to the high-pass filter 16b. The cutoff frequency of the high pass filter 16b is set higher than the frequency of the regular pulse signal. Therefore, the high-pass filter 16b extracts the high-frequency noise component. After the extracted high frequency noise component is amplified by the next amplifier 16c,
Half-wave rectification is performed by the detection rectification circuit 16d, and a signal having only one polarity is obtained. Then, the signal level of the half-wave rectified high frequency noise signal is detected by the level detection circuit 16e.

When the level detection circuit 16e detects a high frequency noise signal having a predetermined signal level or higher, it sends the high frequency noise detection signal to the next latch circuit 16g through the isolation circuit 16f. Latch circuit 1
6g latches and outputs a high frequency noise detection signal in synchronization with a clock signal input from the outside. High frequency EMI
The high frequency noise detection signal output from the detection circuit 16 is displayed on the display unit 13 together with the generation time read from the clock circuit 18.

Therefore, this high frequency EMI detection circuit 1
Reference numeral 6 detects high-frequency EMI noise such as radio waves radiated from an external antenna and high-frequency radio waves radiated from other electronic devices arranged near the antenna.

T input into the pulse noise detection circuit 17
The high-pass filter 17a removes low-frequency noise components from the AMI-encoded pulse signal transmitted on the line 3a, the attenuator 17b attenuates the low-frequency noise component at a predetermined attenuation rate, and the amplified signal is amplified by the amplifier 17c. And the amplifier 17c
The pulse signal output from is subjected to half-wave rectification by the detection rectification circuit 17d to become a monopolar signal having only one polarity. The monopolar signal is detected by the next level detection circuit 17e only as noise pulses that are outside the allowable level range of the signal level of the regular pulse signal, and is input to the next timing generation circuit 17f.

The timing generation circuit detects the rising timing of each input noise pulse signal and sends the rising detection signal to the first rising detection circuit 17h and the second rising detection circuit 17i via the isolation circuit 17g. .. Upon receipt of the rising edge detection signal, the first rising edge detection circuit 17h sends a start signal to the pulse width detecting circuit 17j including, for example, a counter, and sends the first rising edge detection signal to the second rising edge detection circuit 17i. The second rising detection circuit 17i is the first rising detection circuit 17h.
When the rising edge detection signal is received in the state where the first rising edge detection signal is input from, the end signal is sent to the pulse width detection circuit 17j.

Therefore, the pulse width detection circuit 17j measures the noise pulse generation interval. Then, when the measured generation interval coincides with a cycle determined by a specific noise type such as a power supply frequency of 50 Hz or 60 Hz, a pulse noise detection signal is sent to the latch circuit 17k. The latch circuit 17k latches and outputs the pulse noise detection signal in synchronization with a clock signal input from the outside.
The pulse noise detection signal output from the pulse noise detection circuit 17 is displayed on the display unit 13 together with the occurrence time read from the clock circuit 18.

Therefore, this pulse noise detection circuit 1
Reference numeral 7 detects, for example, pulsed noise in which noise pulses are generated at a specific cycle of a power source or the like.

FIG. 4 is a block diagram showing a schematic structure of the normal mode noise detecting section 12 for detecting the normal mode noise on the T line 3b. Although not shown, a normal mode noise detector having the same configuration is also connected to the R line 3a.

The normal mode noise detector 12 is roughly divided into a transformer 19 for impedance matching, which is assumed to be a terminal connected between a pair of signal lines forming the T line 3b, and a terminal between both terminals of the transformer 19. , An abnormal signal level detection circuit 20 for detecting an abnormal signal level in the pulse signal appearing at 1, an abnormal pulse width detection circuit 21 for detecting an abnormal pulse width in the pulse signal appearing between both terminals of the transformer 19, and the detection circuits 20, 21. When the abnormal pulse is detected, the logic waveform storage unit 22 stores the ON / OFF logic waveform of the pulse.

The AMI-coded pulse signal transmitted through the T line 3b and inputted into the abnormal signal level detection circuit 20 via the transformer 19 is inputted into a plurality of comparators 20a. A threshold value is set in each comparator 20a from the comparison value setting circuit 20b. Each of the thresholds is a value indicating to which range the signal level of the pulse signal belongs, and for example, 0.23v (minimum standard), 0,27v (good),
0,4v (good), 0.6v (good). 0.8v (good), 1.0v
It is set as (Good), 1.2v (No), 1.5v (No). Then, each comparator 20 compares the signal level of the input pulse signal with a threshold value and sends the result to the level determination unit 20c. The level determination unit 20c determines the signal level from each comparison result, and outputs a noise pulse detection signal when there is a pulse having a signal level of 1.2v or higher, for example. The noise pulse detection signal output from the abnormal signal level detection circuit 20 is displayed on the display unit 13 together with the time of occurrence. At the same time, the noise pulse detection signal is input to the logic waveform storage unit 22.

Further, the AM transmitted on the T line 3b input into the abnormal pulse width detection circuit 21 via the transformer 19.
The I-coded pulse signal is converted by the bipolar / unipolar conversion circuit 21a into a unipolar signal having only (+) polarity, for example. The pulse signal converted into the unipolar signal is once latched in the data latch circuit 21b in synchronization with the clock signal of the clock oscillator 21d, and then applied to the counters te to 21c.

The counter circuit 21c is the data latch circuit 2
When the pulse output from 1b rises, the clock oscillator 2
The counting of the elapsed time is started based on the clock of the clock signal from 1d. When the pulse falls, the counting of the elapsed time is stopped and the count value is cleared. That is, the counter circuit 21 measures the pulse width of each pulse in the pulse signal. The count value of the counter circuit 21 is input to the long pulse width detection circuit 21e and the short pulse width detection circuit 21f in real time.

The long pulse width detection circuit 21e, the short pulse width detection circuit 21f, and the short pulse interval detection circuit 21g have limit pulse widths TL, TS1, and TS2 from the long / short pulse width / short pulse interval selection condition setting circuit 21h, respectively. Is entered. In the long pulse width detection circuit 21e, the count value of the pulse width input from the counter circuit 21 in real time is the limit pulse width T.
When it exceeds L, a long abnormal pulse width detection signal is output. Further, the short pulse width detection circuit 21f outputs a short abnormal pulse width detection signal if the count value of the pulse width input from the counter circuit 21 in real time is cleared before reaching the limit pulse width TS1.

The long abnormal pulse width detection signal, the short abnormal pulse width detection signal, and the short abnormal pulse interval detection signal output from the abnormal pulse width detection circuit 21 are displayed on the display unit 13 together with the occurrence time. At the same time, each detection signal is input to the waveform storage unit 22. The same applies to TS2.

The logic waveform storage unit 22 always stores the latest logic pulse waveform of the input pulse signals for a fixed time, and when each detection signal is input from the abnormal pulse width detection circuit 21, The logic pulse waveform corresponding to this detection signal is not cleared but stored together with its generation time.

In the ISDN line noise detecting device having the above-described structure, the signal line 3 is caused by, for example, an electric wave radiated from an antenna or another electronic device arranged near the signal line 3. When high-frequency noise is generated in the high-frequency noise, this high-frequency noise is generated by the high-frequency EM in the common mode noise detector 11.
It is automatically detected by the I detection circuit 16 and displayed on the display unit 13 together with the time of occurrence.

Further, if power source noise of 50 Hz or 60 Hz, for example, enters the signal line 3 through the earth, pulse noise generated at a constant cycle determined by the type of the noise is mixed. Therefore, the pulse width detection circuit 17j of the pulse noise detection circuit 17 measures the period, and if the period matches the period corresponding to the preset noise type, it is determined that the pulse noise is present and is displayed together with the occurrence time. It is displayed on the section 13.

Further, the R lines 3a and T which constitute the signal line 3
When normal mode noise occurs between the signal lines on the line 3b, the noise pulse is superimposed on the regular pulse signal. Therefore, the signal level of each pulse of the regular pulse signal is out of the allowable level range, or the pulse width is out of the allowable pulse width range. In such a case, the abnormal signal level detection circuit 20 and the abnormal pulse width detection circuit 21 detect the abnormality caused by the noise pulse, and display it together with the occurrence time. Further, the abnormal logic pulse waveform is also stored in the logic waveform storage unit 22.

As described above, various kinds of noise generated on the signal line 3 connecting the DSU 2 and each terminal 4 can be surely detected, and the kind of the noise is automatically determined. Therefore, the work efficiency of the noise measurement work can be significantly improved as compared with the method in which the worker observes the detected waveform using the conventional oscilloscope or logic analyzer. Further, since the type of noise is also specified, it is possible to easily and efficiently take measures to prevent noise when noise occurs.

Further, in the apparatus of the embodiment, it is possible to automatically store the noise occurrence together with the occurrence time, so that it is not necessary for the worker to constantly monitor this apparatus.

The present invention is not limited to the above embodiment. The abnormal pulse width detection circuit 21 in the embodiment detects only when the pulse width of the pulse signal is longer than the allowable pulse width range (TS1, TS2, TL), when it is short, and when the interval is short.

[0047]

As described above, according to the ISDN line noise detection apparatus of the present invention, each type of noise generated in the signal line is classified into common mode noise and normal mode noise, and each mode noise is further classified. Noise is classified into a plurality of noise types, and the presence or absence of noise generation and the type of generated noise are detected by respective dedicated noise detection circuits. Therefore,
Since the noise generated in the signal line, including its type, can be automatically detected, the work efficiency of the noise evaluation work and the noise generation prevention work that follows can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a common mode noise detector of an ISDN line noise detector according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing an overall ISDN configuration in which the apparatus of the embodiment is incorporated,

FIG. 3 is a schematic diagram showing a main part of a diagnostic device in which the device of the embodiment is incorporated,

FIG. 4 is a block diagram showing a normal mode noise detection unit of the apparatus of the embodiment.

FIG. 5 is a circuit diagram showing a pseudo communication circuit in a common mode noise detector of the apparatus of the embodiment.

FIG. 6 is a diagram showing a general noise pulse waveform.

[Explanation of symbols]

1 ... ISDN exchange, 2 ... DSU (line terminating equipment), 3
... Signal line, 3a ... R line, 3b ... T line, 4 ... Terminal, 8 ...
Diagnostic device, 10 ... Noise detection device, 11 ... Common mode noise detection unit, 12 ... Normal mode noise detection unit, 13 ... Display unit, 15 ... Pseudo communication circuit, 16 ... High frequency EMI detection circuit, 17 ... Pulse noise detection circuit , 19 ... trance, 2
0 ... Abnormal signal level detection circuit, 21 ... Abnormal pulse width detection circuit, 22 ... Logic waveform storage section.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Teruo Kuwahara 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Akio Ochiai 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A common mode noise detection unit (11) for detecting common mode noise input to the ISDN signal line (3, 3a, 3b) from the outside such as a power supply or an antenna, and a signal line in the signal line. An IS including a normal mode noise detecting section (12) for detecting normal mode noise generated between each other and a display section (13) for displaying a detection result of each noise detecting section.
A noise detection device for a DN line, wherein the common mode noise detection section (11) extracts a high frequency noise component included in a signal transmitted on the signal line with a high-pass filter, and extracts the extracted high frequency noise component. High frequency EMI detection circuit (16) that outputs a high frequency noise detection signal when a high frequency noise component of a predetermined level or higher exists
A high-pass filter is used to extract the high-frequency signal component contained in the signal transmitted on the signal line, the counter measures the extraction interval of the high-frequency signal component, and the measured value is determined by the type of noise. And a pulse noise detection circuit (17) for outputting a pulse noise detection signal at a time interval, wherein the normal mode noise detector (12) is an AMI-encoded pulse signal transmitted on the signal line. Abnormal signal level detection circuit that measures the signal level of and outputs a noise pulse detection signal when the measured value is outside the allowable level range (20)
And an abnormal pulse width detection circuit (21) which measures the pulse width of the pulse signal and outputs a noise pulse detection signal when the measured value is outside the allowable pulse width range.