JPS6237578B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission characteristic measurement method for automatically measuring transmission characteristics in a toll line, particularly noise characteristics during a call.

The human ear is extremely sensitive to line noise caused by various factors, and in digital transmission lines in particular, audio is sent through the process of quantization and encoding, so the waveform before quantization may differ during playback. Moreover, it is difficult to quantize at low levels of the voice before quantization, and this difference becomes significant, which often causes distortion noise.Measurement of this noise, that is, measurement of noise characteristics during calls, is necessary. This is one of the important items for maintaining transmission quality.

Conventionally, automatic long-distance line test equipment (commonly known as
ATTM), but it did not have sufficient functionality to measure noise characteristics during calls.
That is, since the noise characteristic during a call is expressed by the signal-to-noise ratio, it is necessary to measure the measurement signal sound level and the noise level separately. Therefore, these must be measured, but the
At ATTM, only the former was done.

In other words, the ATTM consists of an outgoing-only device (OTM) installed at one end of the toll line to be measured and a terminating-only device (TTM) installed at the other end of the toll line.The measurement operation is as follows. This is how it is done. First, OTM sends a measurement signal tone to TTM.
Send control signal tone to send to OTM. OTM
When confirming that the measurement signal tone from the TTM has arrived, it stops sending out the control signal tone and measures the transmission characteristics of the line from the TTM to the OTM (return line). After this measurement is completed, OTM is
The control signal tone is sent to the TTM so that the loop connection between the line (outgoing line) in the direction from OTM to TTM and the incoming line is made at the TTM. Upon receiving the control signal tone, the TTM immediately closes the loop by connecting the outgoing line and the incoming line,
Notify OTM of this using a predetermined specific signal. When the OTM receives the specific signal tone, it sends the measurement signal tone to the TTM. In TTM, the measurement signal sound that has arrived from the outgoing circuit is returned to the incoming circuit. Then, the OTM receives the returned measurement signal sound and measures the transmission characteristics of the round trip line. Then, the OTM obtains the measurement result of the transmission characteristics of the outgoing line by subtracting the above-mentioned measurement result of the return line from the measurement result of the transmission round trip line.

In this way, ATTM measures the return line,
Next, since the outgoing line measurement operation is performed sequentially, the time required for measurement becomes long. In particular, in recent years, the number of telephones owned has increased, the number of various services has increased, and the number of long-distance lines has increased significantly, making it time-consuming.
The method of measuring transmission characteristics using ATTM has difficulty maintaining the high quality of the line, and it is also uneconomical to add ATTM as the number of lines increases.

An object of the present invention is to provide a transmission characteristic measurement method that overcomes these drawbacks.

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

In the measurement method of the present invention, measuring devices having the configuration shown in FIGS. 1 and 2 are provided at both ends of the toll line 1 to be measured that sandwiches the transmission line, and one of them is used as the transmitting device MM which plays a leading role in the measurement procedure. the other is a transmitting device
It is used as a receiving device SM that plays a subordinate role to the MM. Note that FIG. 1 shows a case where a four-wire line is measured as the toll line to be measured, and FIG. 2 shows a case where a two-wire line is measured.

The measuring devices constituting the transmitting device MM and the receiving device SM include oscillators 11 and 31, and a modulator 1, respectively.
2, 32, demodulator 13, 33, measuring device 14, 3
4, measurement signal receiver 15, 35, control section 16, 3
6. It is composed of band pass filters 22, 42 and band elimination filters 17, 37. The measuring devices 14 and 34 include a squaring circuit and an integrator for measuring the effective value of the incoming signal, and an A converting the output of the integrator into a binary number for final numerical dB display.
- Consists of a D converter and a dB converter that stores a numerical dB display corresponding to its output. Further, the control units 16 and 36 control the oscillator 1
A program that stores procedures such as setting the frequency, level, etc. of the measurement signal sound from 1, 31, and controlling the modulators 12, 32, demodulators 13, 33, etc. for exchanging control signals with the partner device. storage section,
a central control circuit that reads and executes the stored contents; the measuring devices 14, 34; the oscillators 11, 31;
It is composed of input/output control circuits for easily coupling with modulators 12, 32, demodulators 13, 33, measurement signal tone receivers 15, 35, etc. Furthermore, the band elimination filters 17 and 37 are used to eliminate measurement signal sounds sent from the other party. Each of the band pass filters 22 and 42 passes only the measurement signal sound sent from the other party.

Based on Figure 3, we will explain the transmission and reception of control signals between the transmitting device MM and the receiving device SM and the flow of measurement operations when measuring the transmission characteristics of the 4-wire line under test shown in Figure 1, especially the noise characteristics during calls. I will explain.

Measured line 1 between transmitting device MM and receiving device SM
In this state, the control unit 16 controls the modulator 12 and starts the receiving device SM from the transmitting device MM side, so that test information 51 necessary for measurement is transmitted to the receiving device SM using a mark and a frequency modulation method. It is sent as a control signal sound consisting of a combination of space frequencies.
This signal is sent from contact b to a of contact 18, through line transformer 20, to toll line 1 to be measured, and demodulated by demodulator 33 through line transformer 40 of receiving device SM. That is, the mark and space frequencies of this control signal are detected by the frequency modulation method. The control unit 36 of the receiving device SM receives the demodulated output signal of the demodulator 33, reads the test information 51, controls the modulator 32, and provides confirmation information for notifying the transmitting device SM that the test information 51 has been confirmed. 52 is returned with a control signal sound. This signal is sent to the toll line 1 to be measured via the line transformer 41 from b to a of the contact point 38, and is demodulated by the demodulator 13 in the same manner as described above via the line transformer 21 of the transmitter MM. The control unit 16 reads this demodulated output signal and sends it to both devices via the toll line 1 to be measured.
It is determined that a data link has been established between MM and SM. The control unit 16 controls the modulator 12 to control specified signal tone transmission information 53 for specifying the frequency and transmission level of the return measurement signal tone to be transmitted from the receiving device SM to the transmitting device MM to the receiving device SM side. Send with a signal tone. This signal enters the control section 36 via the demodulator 33 of the receiving device SM along the same route as described above.

When the control unit 36 determines that the instruction is to send out the measurement signal sound, it switches the contact 38 from b to c, and the oscillator 3
1 to send a return measurement signal sound 54 of the specified frequency and sending level to the transmitter MM, contact 38
From c to a, it is returned via the line transformer 41. This signal is received by the measurement signal sound receiver 15 via the line transformer 21 via the toll line 1 to be measured, and its output is sent to the control section 16. 55 in Figure 3
indicates that this returning measurement signal sound is being sent out.

When the control unit 16 confirms that the return measurement signal sound 54 has been received from the receiving device SM by the output of the receiver 15, it switches the contact 18 from b to c, controls the oscillator 11, and sets the predetermined frequency and transmission level. Outbound measurement signal sound 56 to receiving device SM, contact 18
c, the signal is sent out via the line transformer 20.
Reference numeral 57 in FIG. 3 indicates the outgoing measurement signal sound is being sent out. Further, the control unit 16 controls the receiver 15.
In order to confirm the arrival of the outbound measurement signal tone 54 from the receiving device SM by the output of , and measure the signal-to-noise ratio, first, after the outbound measurement signal tone sending operation is completed,
The contact 19 is set to the a side, and only the return measurement signal sound is passed through the band pass filter 22, and the measuring device 14 is controlled to measure the level of the return measurement signal sound for a predetermined period of time, and then the contact 19 is switched to the b side. The return path measurement signal sound is removed by the band elimination filter 17, and the level of signals other than the measurement signal sound, that is, noise, is measured. The control unit 16 calculates the signal-to-noise ratio from the signal level and the noise level. In Figure 3, 5
8 indicates that this measurement operation is in progress, 58a indicates that a signal tone measurement operation is in progress, and 58b indicates that a noise measurement operation is in progress. As shown in FIG. 3, the measurement signal tone sending operation 57 and the measurement operation 58 overlap in time in the transmitter MM.

On the other hand, in the receiving device SM, the outgoing measurement signal tone 56 arriving from the transmitting device MM is received by the measurement signal tone receiver 35 via the line transformer 40, and its output is sent to the control section 36. The control unit 36 is a transmitter MM
When it is confirmed that the measurement signal sound has arrived, the contact 39 is set to the a side, and only the outgoing measurement signal sound is passed through the bandpass filter 42, and the measuring device 24 is controlled to measure the level of the outgoing measurement signal sound for a predetermined period of time. Then, the contact 39 is switched to the b side, the outgoing measurement signal sound is removed by the band elimination filter 37, and the level of the signal other than the measurement signal sound, that is, the noise is measured. The control unit 36 calculates the signal-to-noise ratio from the signal level and the noise level. 59 in Figure 3
59a indicates that the measurement operation is in progress, 59a indicates that the signal sound is being measured, and 59b indicates that the noise measurement operation is in progress. As shown in FIG. 3, the measurement signal tone sending operation 55 and the measurement operation 59 overlap in time in the receiving device SM.

When the measurement at the receiving device SM is completed, the control unit 36
controls the oscillator 31 to stop transmitting the measurement signal sound to the transmitter MM, and returns the contact 38 from c to b. 60 in FIG. 3 indicates the stop of sending out the measurement signal tone.

The measurement signal tone receiver 15 of the transmitter MM detects this transmission stop and sends a detection signal to the control section 16.

The control unit 16 thereby controls the oscillator 11 to stop sending the measurement signal sound to the receiving device SM, returns the contact 18 from c to b, and switches the modulator 12
control, and sends measurement result sending instruction information 61 to the receiving device SM in the form of a control signal. This signal enters the control unit 36 via the demodulator 33.

The control unit 36 controls the modulator 32 to
Measurement result information of signal-to-noise ratio measured by SM 62
is sent to the transmitting device MM as a control signal. This signal is sent to the control section 16 via the demodulator 13 of the receiving device MM. In this way, the measurement results of the call noise characteristics for the line from the transmitter MM to the receiver SM (outgoing line) and the line from the receiver SM to the transmitter MM (return line) are obtained at the transmitter MM. It will be done.

By sequentially changing the sending levels of the outbound measurement signal tone and the return measurement signal tone and performing the same measurements as described above, it is possible to measure the change in noise during a call with respect to the sending level of the measurement signal tone, that is, the noise level characteristics during a call. Subsequent processing of the measurement results can be transferred to an external device and output to a printer or display.

The above describes the measurement of the 4-wire line under test shown in Fig. 1, but also in the case of the 2-wire line under test shown in Fig. 2, the transmission and reception of signals between the transmitting device MM and the receiving device SM and measurement are performed. The flow of operation is exactly the same.
However, in the case of a two-wire system, the outgoing and returning paths are common, so if the same measurement signal sound is sent on the outgoing and returning paths, if the phase of both signals is 180 degrees out of phase, the signal may be reduced at that position. There is also a 2-wire line under test and measurement equipment (sending device MM and receiving device
Hybrid circuit 23 for connecting SM),
43, but since it is usually difficult to make a hybrid circuit ideally, a phenomenon occurs in which the signal being sent to the other party leaks through the hybrid circuit to the measuring instrument itself, affecting the accuracy of measurement.

For this reason, the frequencies of the measurement signal sound sent out on the outbound path and the measurement signal sound sent out on the return path are made so that they do not have the same frequency. However, if the frequencies are too far apart, they will be affected by the frequency characteristics of the line and cause errors in measurement, so two adjacent frequencies (for example, f _n , f _{n +
1} ) should be used. Also, band elimination filter 1
7 and 37 use filters that remove both the measurement signal sound coming from the other party and the measurement signal sound sent to the other party, so that the measurement signal sound sent to the other party passes through the hybrid circuit to the own device. Even if it leaks, it can be removed. For example, when the frequency of the outgoing measurement signal tone is f _n and the frequency of the return measurement signal tone is f _{n +1} , the characteristics of the band elimination filter 17 on the transmitting device MM side are shown in Fig. 4a, and the characteristics of the band elimination filter 17 on the receiving device SM side are The characteristics of the band elimination filter 37 are shown in FIG. 4b. As shown in FIGS. 4a and 4b, the amount of attenuation of the measurement signal sound to be sent out is made low in order to take into consideration that the hybrid circuit will attenuate to some extent.

As explained above, in the present invention, a transmitting device is connected to one end of the toll line to be measured, a receiving device is connected to the other end,
Control signals necessary for measurement are sent and received between the transmitting device and the receiving device via the toll line to be measured, and an outgoing measurement signal sound is sent from the transmitting device to the receiving device and from the receiving device to the transmitting device. At the same time as the measurement signal sound transmission operation, the transmitting device outputs the return measurement signal sound at different frequencies and at the same time as a frequency that is removed by the band cancellation filter of the other party. measurement signal sound,
In the receiving device, the above-mentioned outgoing measurement signal sound is removed by a band cancellation filter, and the signal other than the measurement signal sound, that is, the noise level is measured to obtain the noise characteristic measurement result during the call, so the following is done. have an effect.

(a) Since the measurements of the outgoing line and the returning line can be carried out at the same time, overlapping in time, instead of being carried out sequentially as in the past, the time required for measurement can be significantly shortened. Therefore, the increased number of toll lines can be measured in a short time, making it easy to maintain transmission quality.

(b) Since different frequencies are sent out as measurement signal sounds from both sides, the line under test is a 4-wire system, a 2-wire system,
Can be measured regardless of wire type. In addition, the measurement signal sound coming from the other party passes through a filter and reaches the measuring instrument, but the frequency of both measurement signal sounds is adjusted so that even if the measurement signal sound sent from the device itself comes around from the hybrid circuit, it does not pass through the filter. Therefore, even in a two-wire line under test, it is possible to eliminate the adverse effect on measurement accuracy caused by the transmission signal going around to the other party.

[Brief explanation of the drawing]

1 and 2 show the configuration for explaining the measurement method according to the present invention, and FIG. 1 shows a 4-wire line under test,
FIG. 2 shows the case of measurement of a two-wire line under test.
FIG. 3 is an explanatory diagram showing the flow of signal exchange and measurement operations between a transmitting device and a receiving device when measuring noise characteristics during a call according to the present invention, and FIG. Characteristics FIG. 4b is a diagram showing the characteristics of the band-stop filter of the receiving device. MM... Transmitting device, SM... Terminating device, 1... Toll line to be measured, 11... Oscillator, 12... Modulator, 13...
Demodulator, 14... Measuring instrument, 15... Measurement signal tone receiver, 16... Control unit, 17... Band elimination filter, 2
3... Hybrid circuit, 31... Oscillator, 32... Modulator, 33... Demodulator, 34... Measuring device, 35... Measurement signal sound receiver, 36... Control section, 37... Band elimination filter, 43... Hybrid circuit, 51... Test information, 52...Confirmation information, 53...Specified signal sound sending information, 54...Return measurement signal sound, 55...Return measurement signal sound in operation, 56...Outbound measurement signal sound, 57...Outbound measurement signal sound in operation, 58, 59...During measurement operation, 60...Stop sending out measurement signal sound, 61...Measurement result sending instruction information, 62...Measurement result information.

Claims (1)

[Scope of Claims] 1. Connecting a transmitting device to one end of the toll line to be measured and a terminating device to the other end, and connecting the transmitting device and the terminating device to each other via the toll line to be measured. The outgoing measurement signal sound sent from the transmitting device to the receiving device and the return measurement signal sound sent from the receiving device to the transmitting device are transmitted and received at different frequencies and to the other party's band elimination filter. Therefore, at the same time as the measurement signal sound sending operation, the transmitting device removes the return measurement signal sound, and the receiving device removes the outbound measurement signal sound, respectively, by the band elimination filter. A transmission characteristic measuring method characterized in that a signal other than the measured signal sound, that is, a noise level is measured to obtain a noise characteristic measurement result during a call.