JPS5835432B2 - Telephone exchange testing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes pulse code modulation PCM technology and time division signal multiplexing T.
The present invention relates to a method of configuring a digitally encoded test signal when testing the operating characteristics of electronic circuit elements such as band limiting circuits and encoder/decoder circuits in a telephone exchange channel system using DM technology.

Unlike telephone exchanges that are based on conventional space division switches, PCM telephone exchanges are electronic exchanges that are realized by combining active electronic circuit elements, making full use of both pulse code modulation PCM and time division signal multiplexing TDM technologies. It is.

These PCM exchanges are revolutionary in that they can easily provide convenient and diverse services to telephone users, and because they can be interconnected via the PCM transmission path, they have helped integrate communications networks. There is hope for future development in that it is possible.

In such communication devices, unexpected failures may occur due to failures or deterioration of characteristics of electronic circuit elements.

Therefore, it is highly desirable to discover failure points early and automatically discover failure points.

FIG. 1 is a basic configuration diagram of a PCM switch implementing the present invention.

In Figure 1, the positions are telephones (#1 to #n), 5
DSW is a space division concentrator switch, HVi hybrid circuit network, As and ARVi transmission and reception electronic circuits (amplifiers).

p wave generator, etc.), G is sampling circuit, DVi distribution circuit, C0D
EC is an encoder-decoder (especially when distinguishing.

COD is an encoder, DEC is a decoder), #S and HWRVi are common lines for the transmitting/receiving system, HWSW is a common line switch, and Jl and J2 are jumpers.

It was a cabinet. Figure 1 shows that the number of time-division multiplexing of PCM signals is m(CH
1, CH2, song -, CHm), and illustrates that the encoder/decoder C0DECI of the set ] is used multiplex in the call on the door side.

Here, the operation of the PCM switch will be explained with reference to FIG.

The 5DSW connects n telephone lines and a TEST line (described later) to any time-division channel system (CHI, CH2, -
---CHm) is a switch network that connects to 1, for example #
When a call is made between the location 1 and the location #, the location #]V'1SDS
It is connected to the CHI system through route R1 of W, and S
It is connected to the CH2 system through route R2 of the DSW.

The transmitted audio from CHI system H to route P5. As
, G, and enters C0DI, where it is PCM encoded.

This PCM signal. HWs, switch a button, H
It enters DECI via WR and is decoded.

This decoded audio signal is transmitted to the CH2 system, AR,...
The received audio goes through H2 and is placed at #.

Similarly, the transmitted audio from T E L + k is C0DEC
] and becomes the received audio of position #I.

Also, there are other calls. The same applies to the case where it is performed via C0DEC2 and switch points ci- and d.

Next, a method for testing the operation of the communication path system will be explained.

Although many complex electronic circuit elements are used in the communication path system of a PCM switch, consideration must be given to ensuring sufficient reliability when designing the installation.

However, consideration must also be given to the early detection of unexpected obstacles.

In order to detect the occurrence of a failure, testing must be performed in some way at all times, even under normal circumstances.

The test will provide ``confirmation of normality''.

The result of most of the tests is ``abnormal L jj,'' and the case where L''''normal recognition'' is not obtained is ``abnormal.''

Therefore, for a test to obtain "confirmation of normality"("abnormalL"), a simple and short-time method 75 (requiring a small number of steps in the test control system) is required.

A PCM switch is essentially a four-wire system (the transmitting system and the receiving system are composed of independent communication path systems), and for the communication path system test, one communication path and one transmission system are required. It is common to treat the receiving system and the receiving system separately.

If it is possible to test the L steering wheel and the transmitting/receiving system at the same time, the above-mentioned purpose (to easily confirm normality) can be achieved.

In FIG. 1, a test device TEST, and.

The TESTK associated signal path is the main operational part of the present invention.

- As an example, the signal path during CHI system testing will be explained.

The test signal is output from point X of TEST in PCM code format.

HWs, via switch points e and f.

Supplied to DECI.

The test signal is decoded by DECl and provided to 'CH via AR.

At this time, CHI system H is connected to TESTK through path R3 of 5DSW in advance.

The decoded test signal is provided to TEST.

It is looped back at TEST and sent back to H via route R3.

This test signal is of the CHI system. and CO via G
D] and PCM encoded.

Furthermore, this encoded test signal is supplied to TEST via switch points a and g.

Similarly, when testing CH2 system, H of CH2 system is 5D
Connected to TEST through path 4 of SW.

Next, the operation of the test apparatus TEST will be explained with reference to FIG.

Ht is a hybrid circuit network. COD, is encoder, DEC
t is a decoder, A1. A2゜A3 is an amplifier, sl, s2.
s3,54Vi switch.

5GVi test signal test concentrator, DET is test signal receiver.

During the test, 51tS2. S3. It is assumed that S4 is fixed to the path shown in FIG.

The test signal in PCM code format supplied from the SG of TEST is supplied to the HWs (Figure 1) from terminal .

The output of DECl is applied to the terminal q of TEST via CHI, AR, H, and route R3 of 5DSW.

TEST sets the signal at terminal q to Hl. So, A1. S2. H
5DSW is returned via route R3, and C is sent via route R3.
It is applied to C0DI through H, As, and G of HI.

The signal is now encoded again into a PCM signal and sent to the HWs.
.

The test signal, which is printed on terminal y of TEST via HWSW and HWR and has gone around the exchange, is supplied to DET of TEST.

If the operation and electrical characteristics of the electronic circuit element in the system under test are "normal", the signal detected by the DET will be:

It should match the test signal sent from the SG extremely well, and DETVi has a function to verify the degree of matching.

Normally, most communication channels should be operating normally, and each channel will be confirmed to be "normal" one after another.

If 6 abnormalities are found in the CHI system test, the possibility of failure is (]) CHI transmission system (ks, G), (2) CODI system, (3) DECI system, (4) CHI reception system (D t AR).

In this case, the CH2 (or CH3 to CHm) system will be tested and the possibility of failure will be subdivided.

If the CH2 test is 1 normal, then (2)
, (3) Vi is “normal”, and there is a possibility of “abnormal” + “IE” in (1) or (4) ((5)).

If the CH2 system test is "abnormal", either (2) or (
There is a possibility that 3) is “abnormal” ((6))
.

Therefore, in either case, an attempt must be made to independently test either the transmitting system or the receiving system of the CHI system.

FIG. 3 is an example of a test signal used to perform such a test.

The test signal waveform expressed in analog form is f.

Then, this signal consists of three types of sine waves f1+f3yf
, is represented by the addition '8--shape wave.

As a method for selecting the three frequencies, U) is effective if fl is used for testing the low frequency region, f3 is used for testing the mid frequency region, and f is used for testing the high frequency region. In addition, the configuration of the SG is such that there is a simple integer ratio between the three frequencies (b), and there is also a simple integer ratio between the three frequencies and 8KHz, which is the sampling frequency of the audio signal (c). This is effective for simplifying (specifically, reducing the capacity of the ROM shown in FIG. 4, which will be described later).

In order to satisfy these conditions (A, 22, B, and C), conventionally f
l is 333.3333Hz sine wave s f3 is 1000
．． A 0 Hz sine wave is used, and f9 is used as a 3000.0 Hz sine wave.

The test signal in PCM code format is f.

Assuming p, fop is obtained by sampling f at each point from 0 to 23 on the time axis as shown in FIG. 3, and PCM encoding each sample value.

These PCM encoded sample values are repeated using the basic cycle shown in Figure 3 as one cycle, and the actual generation method is to store these 24 types of PCM codes in a read-only memory (see Figure 4, which will be described later). This is obtained by cyclically reading data from the ROM).

Such a test signal f.

p appears as the output of SG in Figure 2, and DEC
, the test signal f is supplied to the cutting edge of DEC1.
, appears.

However, in reality, the operation of the CODEC shown in FIG. 1 has a companding characteristic (in the field of PCM communication, the standard laws of μ law and A law are common), so f, (!
:f, There must also be a relationship that reflects the companding characteristics.

In FIG. 3, fo is fl, f3. Although we have illustrated the case where it is expressed as an addition composite wave of f9, as a test signal, f
l, f3. The purpose can also be achieved by using f9 single-sine wave gold PCM encoding.

However, by using the Calo calculation summation wave. It becomes possible to perform tests for all three frequencies simultaneously, and the time required for testing can be shortened.

Next, test 1 test signal f.

We will explain the specific method of occurrence of .

FIG. 4 is a detailed diagram of the SG portion in FIG. 2.

CNTsV'i is a counter that counts the sampling period clock, and is a "read-only memory" addressed by the contents of ROMViCNTs.

The 24 types of PCM codes shown in FIG. 3 are stored in advance in the ROM, and the PCM codes are sequentially output according to address designations from the CNTs.

These code sequences are the test signal f. . becomes.

Next, the test signal receiver DET will be explained.

The basic operation of DET is to test whether three frequency components exist within a specified signal level range in the received test signal by performing discrete Fourier transform DFT or digital flow DF. That's true.

FIG. 5 a shows a method of configuring a DET using the ViDFT method, and FIG. 5 shows a method of configuring a DET using the DF method.

NL is a code converter that converts a PCM code encoded by non-linear companding into a linear encoded format, DFTCU, PCM
A discrete Fourier transform circuit that detects frequency components of f□y f3 y f9 from a code sequence, DFC is also a digital wave circuit that performs the same function as DFTC, DCNij
, is a determiner that determines whether each frequency component is detected within a specified level fluctuation.

Although the signal is low, the conventional test signals (fl, f3.f,) have the following drawbacks.

In other words, in conventional test signals, the harmonic distortion components (generated by disturbances) in the communication line system are the same as the test signal acid content! , it is difficult to visually test the demodulated test signal using an oscilloscope, and furthermore, the quantization level of the KCODEC cannot be exceeded.

That is, according to the conventional technology, fl:fs2f9-1=
329, and since the test signal itself has an odd harmonic relationship, it is difficult to separate the distortion component and the test signal.

A long time ago.

f in Figure 3. Because the characteristics of the waveform are not clear, it is difficult to visually evaluate the waveform distortion.

Furthermore, the number of samples is small (24 in the case of Figure 3), and C0
The number of quantization steps in DEC (usually Vi256 for 8-bit encoding) is much smaller than K.

In addition, the number of samples in L is a simple integer ratio, fl: f3: f, so the basic period of the synthetic liquid is short <, When sampling at 8 KHz (period 125 μs), the period of one synthetic liquid is 125 μS
This means that X24=3mS.

Therefore, the present invention improves the drawback described in E of the prior art, and under the above-mentioned conditions of 12 ports and C, the harmonic distortion component (generated due to disturbance) of the 1-channel system becomes the test signal component. Select the frequency components of the test signal so that they are not the same), use a waveform that allows a certain degree of evaluation when visually testing the demodulated signal of the test signal with an oscilloscope, etc. (e), and select the frequency components of the C0DEC. The object of the present invention is to provide a method for testing an exchange using a test signal that satisfies the following three conditions: (1) to enable as many conversion levels as possible;

According to the present invention, the test signal waveform x(t)ld expressed in analog form is as follows.

x(t) = sin 2πfat-5in2πf bt
+ sin 2πfat(1) −Lcos2π(f b−f a) t−−cos 2
π(fb+fa)t2 2 (1)' -)-sin2πfat On the other hand, the first term of Equation 1 (1) is a carrier suppressed amplitude modulated wave with -fa as the modulating wave and fb as the carrier wave. The term is the modulated wave itself.

Here, fa and fb are selected especially when the modulated wave and the upper side band are near the lower limit and the upper limit of the passband of the telephone.

For example, fa is 312.5Hz, fb is 3078.
By setting it to 125Hz, the L sideband wave is 3390.62
5Hz, and conditions 1 and 2 are satisfied.

It was. In this case, the number of samples is 512, which satisfies the condition.

Furthermore, the characteristic that the envelope of Equation (1) is expressed as shown in Figure 6 is characterized by the fact that it has a large effect on waveform distortion with respect to the amplitude distortion and phase distortion of the communication channel system. Ho is satisfied.

Note that each numerical value in L was obtained by determining the door so that 8000X has no integer divisor, so the number of samples is 5.
12 is the period.

As can be seen from FIG. 6, Equation (1) is characterized by a large probability distribution of amplitude values near the 0 level.

In order to test a non-linear CODEC with companding characteristics (quantization steps are concentrated near the 0 level), the conditions must be satisfied by more elements.

As explained above, according to the present invention, the harmonic distortion components (generated due to disturbances) in the communication line system are not the same as the test signal components, and the demodulated signal of the test signal can be visually observed with an oscilloscope or the like. It is possible to use a waveform that can be evaluated to a certain extent when testing, and it is also possible to obtain the effect that the quantization level of KCODEC can be as high as 9.

Therefore, by applying the test method according to the present invention,
Even if the PCM switch is in operation, faults can be detected early by sequentially performing automatic tests starting from non-calling nodes.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of a PCM switch, Figure 2 is a configuration diagram showing an example of a test device, Figure 3 is a waveform diagram showing all examples of conventional test signals, and Figure 4 is a diagram of a test signal generator. 5A and 5B are block diagrams of a Vi test signal receiver, and FIG. 6 is a waveform diagram of an envelope of a test signal according to the present invention.

Claims (1)

[Claims] 1. Pulse code modulation technology PCM and time division signal multiplexing technology T
For communication path system testing of telephone exchanges based on DM,
A digitally coded test signal is generated and supplied as an input to the telephone exchange, and an analog format signal output from the telephone exchange corresponding to the digital code is looped back and inputted to the telephone exchange again. In a method for testing telephone exchanges, the digitally encoded signal is received again as an output from the telephone exchange as an output, and the degree of coincidence between the input and output is detected. It is sampled, quantized, and encoded at an interval of 8 kHz from the additive composite wave of a carrier suppressed amplitude modulated wave and a modulated wave, and the modulated wave and upper sideband are within the passband of the telephone signal and It is characterized in that the frequencies of the modulated wave and the carrier wave are selected so as to be close to the lower and upper limits of the passband frequency. Test methods for telephone exchanges. 2 The frequencies of the modulating wave and carrier wave are 312.5Hz and 3, respectively.
The method for testing a telephone exchange according to claim 1, wherein the frequency is 078.125Hz.