JP2510009B2 - Telephone line eco-measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is an echo in a call system in which each terminal device is connected to each coupler inserted in a four-wire communication line via a two-wire communication line. The present invention relates to an echo measuring device for a communication line for measuring the noise.

[Prior Art] For example, a general telephone call system using a telephone is the sixth
It is configured as shown in the figure. A call signal transmitted and received by each terminal device 1 is transmitted through the two-line type call line 2 to the telephone station 3
It is input to a coupler (hybrid circuit) 4 therein, and is separated into a transmission signal and a reception signal by this coupling circuit 4 and is input to the exchange 6 via a 4-wire communication line 5. Exchanger 6
The call signal input to is transmitted to the transmission device 8 via the trunk 7 when the call destination is a place other than the exchange 6. The transmission device 8 communicates the input call signal to the telephone station 3 of the call destination via various transmission lines 9 such as optical communication, sanitary communication, and microwave communication.

In this case, the impedance matching cannot be perfectly achieved in the coupler 4 connected to the 2-wire type call line 2 and the 4-wire type call line 5, so that the call signal input to the coupler 4 is completely matched. Is not transmitted to the side and a reflected wave is generated. Therefore, the reflected wave is input as an echo to the terminal device 1 on the transmitting side and the terminal device 1 on the receiving side, which is very annoying. In the case of short-distance call, the call signal and the echo signal are almost overlapped, so no problem occurs, but in the case of long-distance call such as international call, the call signal and the echo signal can be heard separately. , Becomes a problem.

Therefore, in order to suppress this echo, it is necessary to measure the echo accurately. As shown in FIG. 7 (a), the echo includes the echo of the sender heard by the terminal device 1a on the transmitting side, and as shown in FIG. 8 (a), the terminal device 1b on the receiving side.
There is a listener echo that can be heard at.

Regarding the echo on the transmitting side, as shown in FIGS. 7 (a) and 7 (b), when the transmitting signal a is transmitted from the terminal device 1a on the transmitting side to the two-wire communication line 2a, The received reception signal b includes the side tone flowing from the transmitter in the terminal device 1a to the receiver and the echo of the transmitter reflected by the coupler 4b connected to the receiver's two-wire communication line 2b. . Therefore, the time from the start time of the transmission signal a to the start time of the talker echo in the reception signal b is the echo delay time Tds. In addition, the amplitude As of the transmitted signal and the amplitude Aes of the echo of the talker
The ratio of and is the echo attenuation.

Regarding the echo on the receiving side, FIG. 8 (a) (b)
As shown in Fig. 7, when the transmitting side terminal device 1a sends the transmitting signal a shown in Fig. 7 (b) to the two-wire type communication line 2a, the receiving side receives the reception via the two-line type communication line 2b. In addition to the direct reception signal corresponding to the transmission signal a, the reception signal c received by the terminal device 1b on the other side is reflected by the two-wire communication line 2b on the reception side and goes around the four-wire communication line 5. Includes listener echo. Therefore, in this case, the time from the start time of the direct reception signal to the start time of the receiver echo in the reception signal c is the echo delay time Tdr. Further, the ratio of the amplitude Ar of the direct reception signal and the amplitude Aer of the receiver echo is the attenuation amount of the echo.

Then, in the case of measuring the speaker echo, as shown in FIG. 9, an oscillator 10 and an oscilloscope 11 are connected instead of the coupler 4a on the transmitter side, and the oscillator 10
The transmission signal a shown in FIG. 7B is directly applied to the 4-wire communication line 5, and the reception signal b shown in FIG. 7B is received by the oscilloscope 11 and displayed on the CRT display tube. I am trying to do it.

When the receiver echo is measured, as shown in FIG. 10, an oscillator 12 and an oscilloscope 13 are inserted in one of the four-wire communication line 5, and the oscillator 12 is used as shown in FIG. The transmission signal a shown in the figure is directly applied to the 4-wire communication line 5, and the oscilloscope 13 receives the receiver echo in the reception signal c shown in FIG. 8B and displays it on the CRT display tube. I am trying.

[Problems to be Solved by the Invention] However, as shown in FIG. 9 and FIG. 10, the following problems to be solved are still to be solved in an echo measuring apparatus that measures an echo using oscillators 10 and 12 and oscilloscopes 11 and 13. There was such a problem.

That is, since each echo delay time Tds, Tdr described above from the signal waveform of each received signal b, c displayed on the CRT display screen of the oscilloscope 11, 13, is visually observed, a large reading error, It is difficult to obtain high measurement accuracy. In particular, each echo waveform is often significantly distorted compared to the transmitted signal waveform, so it is not possible to clearly set from which part of each echo waveform the delay time is measured, which further reduces measurement accuracy. To do.

In addition, since the echo waveform is greatly distorted and the signal waveform may change constantly, it is difficult to obtain an accurate amplitude of the echo waveform. It was difficult to get.

Furthermore, in the measuring device of FIG. 9 and FIG.
The transmission signal a is directly applied to the 4-wire communication line 5 without passing through the 2-wire communication line 2a and the coupler 4a, and the reception signals b and c are applied.
Also, the oscilloscope 1 without using the 2-wire communication lines 2a and 2b
It is directly detected from the 4-wire communication line 5 with 1,13.

Therefore, with each terminal device 1a, 1b connected, the feeling of the echo actually heard by the sender or the receiver via each terminal device 1a, 1b will be different, and the actual echo phenomenon will be faithful. There are problems that are not always measured.

The present invention has been made in view of the above circumstances, and removes only the terminal device and applies a transmission signal to the two-wire communication line on the transmitting side to transmit the signal via the four-wire communication line. Received signal or 4 that returns to the 2-wire communication line on the transmitting side
By receiving the reception signal sent around to the two-line communication line on the receiving side after making a round of the line communication line and obtaining the cross-correlation waveform of the envelope waveform of this reception signal with respect to the reference pulse signal waveform of the transmission signal , The echo delay time and the echo attenuation amount can be measured accurately, and the echo echo measurement device and the receiver echo measurement device that can measure more accurate echo can be measured under the condition that is closer to the actual echo phenomenon. The purpose is to provide.

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a plurality of couplers are inserted in a 4-wire communication line formed in a closed loop, and a 2-wire communication line is connected to each of the couplers. In the talker echo measurement device that measures the attenuation amount and delay time of the echo generated in each coupler in the communication system to which each terminal device is connected, the sine wave signal having the voice domain frequency is used as the reference pulse signal. For the transmission signal input through the transmission signal generating circuit that applies the transmission signal amplitude-modulated by the pulse waveform of the above to the transmission side two-wire communication line and the transmission side two-wire communication line From the envelope waveform detection means for detecting the envelope waveform of the reception signal, the coupler for transmitting the transmission signal to the two-wire communication line and receiving the transmission signal, and the envelope waveform detected by the envelope waveform detection means. A transmission signal removing means for removing the transmission signal that has passed through the coupler, and a cross-correlation waveform between the envelope waveform after the transmission signal is removed by the transmission signal removing means and the reference pulse signal waveform. Cross-correlation calculating means, maximum value detecting means for detecting the maximum value and position of the cross-correlation waveform calculated by this cross-correlation calculating means, maximum value position detected by this maximum value detecting means and reference pulse A delay time detecting means for detecting a difference from the signal waveform position as an echo delay time, and an attenuation amount calculating means for calculating an echo attenuation amount from the amplitude of the transmission signal and the maximum value of the cross-correlation waveform. is there.

Another invention is a receiver echo measuring apparatus for measuring the attenuation amount and delay time of the echo generated in each coupler on the receiving side, and in addition to the above-mentioned transmission signal generating circuit, a two-wire type call on the receiving side. Envelope waveform detecting means for detecting the envelope waveform of the reception signal with respect to the transmission signal input through the line, the reference pulse signal generating circuit for generating a reference pulse signal having the same pulse width as the reference pulse signal, and this reception signal Cross-correlation calculating means for calculating a cross-correlation waveform between the signal waveform of the reference pulse signal output from the side reference pulse generating circuit and the envelope waveform detected by the envelope waveform detecting means, and the cross-correlation calculating means. Maximum value detecting means for detecting the maximum value of the cross-correlation waveform and its position, and the second largest next value of the cross-correlation waveform and the next value for detecting its position Output means, delay time detection means for detecting the difference between the maximum value position and the next value position in the cross-correlation waveform as an echo delay time, and attenuation amount calculation means for calculating the echo attenuation amount from the maximum value and the next value. It is equipped with and.

[Operation] In the speaker echo measuring apparatus configured as described above, the transmitting signal is applied from the transmitting signal generating circuit to the two-wire communication line on the transmitting side. Then, the envelope waveform of the reception signal input to the 2-wire communication line on the transmitting side again via the 4-wire communication line is detected. Since the envelope waveform includes a transmission signal leaking from the transmitter to the receiver, the transmission signal is removed from the envelope waveform. Then, the cross-correlation waveform with respect to the reference pulse waveform of the transmission signal of the envelope waveform after the removal is obtained. In general, the maximum value of the cross-correlation waveform occurs at the position where the correlation value is the highest, so it becomes a singular point indicating the start position of the envelope waveform with respect to the reference pulse waveform. Therefore, the difference between the start position and the maximum value position of the reference pulse signal becomes the echo delay time. Similarly, since the maximum value can be regarded as the average amplitude of the envelope waveform, the echo attenuation amount is calculated from this maximum value and the amplitude value of the transmission signal.

Further, in the receiver echo measuring apparatus, the transmitter signal is applied from the transmitter signal generating circuit to the two-wire communication line on the transmitter side as in the transmitter echo measuring apparatus. Then, the envelope waveform of the reception signal transmitted to the 2-wire communication line on the reception side through the 4-wire communication line is detected. It should be noted that this envelope waveform includes a direct reception signal corresponding to the transmission signal and an echo signal that makes a round around the 4-wire communication line. A cross-correlation waveform for the reference pulse waveform output from the receiver-side reference pulse signal generator of the envelope waveform is obtained. Then, this time, the maximum value corresponding to the direct reception signal of the cross-correlation waveform and the second largest next value corresponding to the echo signal are detected. Therefore, the difference between the maximum value and the next value becomes the echo delay time, and the ratio between the maximum value and the next value becomes the echo attenuation amount.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a speaker echo measuring apparatus according to an embodiment. The same parts as those in FIG. 7 are designated by the same reference numerals.

The digital sine wave signal d output from the digital sine wave signal generation circuit 21 and having the frequency f _V in the voice region is amplitude-modulated by the reference pulse signal e output from the reference pulse generation circuit 23 by the AND gate 22 and D The / A converter 24 applies the analog transmission signal g to the coupler (hybrid circuit) 25. As shown in FIG. 2, the reference pulse signal e has a signal waveform in which a pulse having a width T ₀ repeats at a cycle T ₁ .
The pulse width T ₀ is set sufficiently shorter than the expected echo delay time Tds, and the period T ₁ is set sufficiently longer than the echo delay time Tds.

Therefore, the digital sine wave signal generating circuit 21, the reference pulse generating circuit 23, the AND gate 22, and the D / A converter 24 are
Constitutes a transmission signal generation circuit 26.

The transmission signal g input to the coupling circuit 25 is transmitted to the 4-wire communication line 5 through the 2-wire system 2-wire communication line 2a and the coupler 4a on the transmitting side. The summation signal g sent to the 4-wire type call line 5 is input to the receiver side terminal device 1b via the receiver side coupler 4b and the 2-line type call line 2b, and is reflected by the receiver side coupler 4b. Then, it returns to the 4-wire type call line 5 again and is input as a talker echo signal to the 2-wire type call line 2a on the transmitting side through the coupler 4a. Then, the talker echo signal input to the two-wire communication line 2 a is input to the A / D converter 27 as the reception signal h via the coupler 25. This received signal h
As shown in FIG. ₂ , in addition to the talker echo signal h ₂ , the transmission signal g output from the transmission signal generation circuit 26 is attenuated by the coupling circuit 25 by, for example, about 6 dB. The speech signal h ₁ is included.

The A / D converter 27 samples the reception signal h input by the sampling signal of the frequency f _S (cycle T _S ) output from the oscillator 28 and converts it into, for example, an 8-bit digital reception signal. The value x of the reception signal h output from the A / D converter 27 in each cycle T _S is squared (x ² ) by the squaring unit 29.
The received signal h converted into an instantaneous power value by the squaring circuit 29 is envelope-detected by the next envelope waveform detecting section 30 and becomes an envelope waveform signal i shown in FIG.

The digital envelope waveform signal i output from the envelope waveform detection unit 30 is resampled by the resampling unit 31. The resampling unit 31 is supplied with a sampling signal of frequency f _{P obtained} by dividing the sampling signal of frequency f _S output from the oscillator 28 into 1 / N _P by the frequency divider 32. Therefore, the envelope waveform signal i has a rougher signal waveform.

The envelope waveform signal output from the resampling unit 31 is input to the next averaging processing unit 33. In addition to the sampling signal output from the frequency divider 32, the averaging processing unit 33 includes a rising edge detection circuit 34 for detecting the rising edge timing of the pulse of the reference pulse signal e output from the reference pulse generation circuit 23. The output trigger signal is input. Further, in the averaging processing unit 33, a memory 33a for storing each value X _t at each time position t input at each cycle T _P from the trigger signal input time is formed. Further, an addition counter for counting the trigger signal and a time position counter for counting each time position t are formed.

Whenever a sampling signal is input, the memory
The value X _t input to the area indicated by the time position counter in 33a is added, and the value of the time position counter is incremented.
Then, when the trigger signal is input, the value of the time position counter is reset, and the number of additions of the addition number counter is counted up. Then, when the number of times of addition of the number-of-addition counter reaches a predetermined number of times, such as 10 times, which is set in advance, each value X _t stored in each time position area of the memory 33a is divided by the predetermined number of times to calculate the average envelope waveform k. Output as.

The average envelope waveform k output from the averaging processing unit 33 is input to the next transmission / reception signal removal unit 35. An inverted signal obtained by inverting the reference pulse signal e by the inverter 36 is input to the transmission signal removing unit 35. Then, as shown in FIG. 3, each time position in the time corresponding to the time (T ₀ + α) obtained by adding the grace time α to the pulse width T ₀ corresponding to the L level of the inverted signal in the average envelope waveform k. t
Each value X of is removed to obtain a corrected envelope waveform m.
That is, the average waveform k ₁ from the envelope waveform k transmission signal h ₁ is removed, leaving the waveform k ₂ of the echo signal h _2.

The corrected envelope waveform m output from the transmission signal removal unit 35 is input to the next mutual clearance calculation unit 37. Also, A / D
The converter 28 converts the reference pulse signal e into the frequency from the frequency divider 32.
It is converted into a digital reference pulse waveform n using the sampling signal of f _P and applied to the mutual clearance calculation unit 37. Then, the mutual clearance calculation unit 37 determines that the corrected envelope waveform m
The mutual transmission waveform o with respect to the reference pulse waveform n is calculated. That is, in this mutual transmission waveform o, the peak o ₂ showing the maximum value Ae occurs at the time position t ₂ corresponding to the peak value of the waveform m ₂ in the corrected envelope waveform m.

The mutual phase transfer waveform o output from the mutual transfer calculating section 37 is detected by the maximum value detecting section 38 by the maximum value Ae and its time position.
t ₂ is detected. Then, the time position t ₂ is sent to the delay time detector 39. The delay time detection section 39 detects the time difference between the time points t ₂ of the rising time position t ₀ and the maximum value Ae of the reference pulse waveform n a (t ₂ -t ₀₎ as an echo delay time Tds.

Further, the maximum value Ae detected by the maximum value detecting unit 38 is converted into a unit of decibel (Ae) dB by the logarithmic converting unit 40 and then sent to the attenuation amount detecting unit 41. The attenuation amount detection unit 41 uses the transmission signal g
A value (A ₀ ) dB obtained by decibel-converting the amplitude A ₀ of is stored, and the difference [(Ae) dB− (A ₀ ) dB] dB between the two is output as the echo attenuation amount E (dB).

In the case of the transmitter echo measuring apparatus configured in this way, the corrected envelope obtained by detecting the envelope waveform of the reception signal h with a digital value and further removing the waveform k ₁ resulting from the transmission signal g from this envelope waveform. The waveform m is calculated, and the cross-correlation waveform o between the corrected embedding waveform m and the reference pulse waveform n of the reference pulse signal of the transmission signal is calculated.
The calculated cross-correlation waveform o is regarded as a waveform that replaces the echo signal h ₂ , and the echo delay time Tds and the echo attenuation amount E (dB) are calculated.

Therefore, for example, the echo signal h ₂ included in the reception signal h ₂
Even if is distorted, by calculating the cross-correlation waveform o, it is possible to specify the time position t ₂ showing the maximum value Ae as the starting point of the waveform m ₂ corresponding to the echo signal h ₂ of the envelope waveform m. Therefore, the calculation accuracy of the echo delay time Tds does not decrease.

The maximum value Ae is enveloped waveform m ₂ of the echo signal h ₂
Since it can be regarded as the average value of, the measurement accuracy can be significantly improved as compared with the case where the amplitude value is visually detected by the conventional oscilloscope 11.

In this way, each measurement accuracy can be significantly improved as compared with the conventional measurement device. Further, in the embodiment, since using the average envelope waveform k of an envelope waveform signal i obtained by averaging a plurality of echo signals h ₂ by averaging processing section 33 can be further improved the accuracy of measurement.

Further, the transmission signal g is applied to the two-wire type communication line 2a, and the reception signal h via the four-line type communication line 5 is received via the two-line type communication line 2a connected to the coupling circuit 4a. Because
The echo delay time Tds and the echo attenuation amount E are obtained in a state closer to the actual use state.

FIG. 4 is a block diagram showing a schematic configuration of a receiver echo measuring apparatus according to an embodiment of the present invention. The same parts as those in the embodiment of FIG. 1 are designated by the same reference numerals.

In this embodiment, the transmission signal generator circuit 26 applies the transmission signal g shown in FIG. 2 to the two-wire communication line 2a on the transmitting side. Then, the transmission signal g is input to the 4-wire type call line 5 via the coupler 4a, and is input to the receiver's 2-line type call line 2b via the receiver-side coupler 4b. Then, an A / D signal is received as a reception signal p via a coupler (hybrid circuit) 51.
Input to the converter 27.

As shown in FIG. 5, the reception signal p input to the A / D converter 27 includes, in addition to the direct reception signal p ₁ by the transmission signal g directly input from the combiner 4b, the combiner 4b. Is reflected by
4-wire communication line 5 reflected by the coupler 4a on the opposite side
It includes the echo signal p ₂ that makes one round and the echo signal p _{3 that} makes another round.

Then, the received signal p is converted into a digital received signal by the A / D converter 27, further converted into an instantaneous power value by the squaring operation unit 29, and the envelope waveform detection unit 30 performs envelope detection. Becomes an envelope waveform signal. Further, the resampling unit 31 performs resampling at a coarse sampling cycle, and the averaging processing unit 33 averages a plurality of envelope waveform signals.

The reference pulse signal used for this averaging processing is a reference pulse signal having the same pulse width T ₀ as the reference pulse signal e on the transmitting side, and is output from the receiving side reference pulse generating circuit 52 provided on the receiving side. Supplied. Therefore, it is asynchronous with the reference pulse signal e on the transmitting side.

The average envelope waveform output from the averaging processing unit 33 is removed by the next unnecessary waveform removing unit 53 to remove the unnecessary signal component t directly included in the vicinity of the received signal p ₁ and the cross-correlation calculating unit 37 as the corrected envelope waveform q. Sent to. The mutual clearance calculating unit 37 calculates the mutual clearance waveform s shown in FIG. 5 with respect to the reference pulse waveform r output from the A / D converter 28 of the corrected envelope waveform q.

As shown in the figure, the calculated mutual transmission waveform s has a peak q ₁ of the direct reception signal in the corrected envelope waveform q.
And peaks s ₁ , s ₂ , s ₃ are generated at time positions t ₁ , t ₂ , t ₃ corresponding to the peaks q ₂ , q ₃ of each echo signal.

Then, the mutual transmission waveform q is detected by the maximum value detection unit 54,
The maximum value A ₁ and its time position t ₁ of the maximum peak q ₁ is detected, the following values A ₂ of the larger peak q ₂ to the second in the next value detector 55
And the time position t ₂ is detected. Thus, the echo delay time Td shown in the time from the time position t ₁ of the maximum value A ₁ at delay time detection section 56 to the time position t ₂ of the following values A ₂ (t ₁ -t ₂₎
r is calculated.

Further, the maximum value A ₁ and the next value A ₂ are the logarithmic transformation unit, respectively.
Attenuation calculation section 5 after conversion to decibel units at 57 and 58
Sent to 9. The attenuation amount calculator 59 subtracts them to obtain an echo attenuation amount E = [(A ₁ ) dB− (A ₀ ) dB] dB.

With the receiver echo measuring device having such a configuration, since the receiving signal p is received via the two-wire communication line 2b on the receiving side, as in the conventional device shown in FIG. The echo measurement can be performed in a state that is closer to the actual state without the need to intervene in the middle of the call line 5. Further, since the cross-correlation waveform q is calculated by the same method as in the previous embodiment to obtain the echo delay time Tdr and the echo attenuation amount E on the receiving side, almost the same effect as in the previous embodiment is obtained. be able to.

The present invention is not limited to the above embodiment. In each of the embodiments, each of the squaring unit 29 to the attenuation amount calculating unit 59 has an independent circuit configuration. However, each of these functions is incorporated into a control program and is executed by software using a signal processor or the like. It is also possible.

[Effects of the Invention] As described above, according to the present invention, only the terminal device is detached, and the transmission signal is applied to the two-wire communication line on the transmitting side, and the transmitter echo measuring device has four Receives the received signal returning to this two-wire communication line via the two-wire communication line, and in the receiver echo measuring device, goes around the four-wire communication line to the two-wire communication line on the receiving side. Receiving the received reception signals, creating envelope waveforms of the reception signals respectively, calculating the mutual transmission waveform with respect to the reference pulse signal waveform of the transmission signal of this envelope waveform, and using this mutual transmission waveform to echo The delay time and the echo attenuation amount are calculated. Therefore, the measurement accuracy of the echo delay time and the echo attenuation amount can be greatly improved, as compared with the conventional device that was visually measured using an oscilloscope or the like. Furthermore, it is possible to measure under conditions that approximate the actual echo phenomenon, and more accurate echo can be measured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a speaker echo measuring apparatus according to an embodiment of the present invention, FIGS. 2 and 3 are waveform diagrams showing the operation of the apparatus of the same embodiment, and FIG. 5 is a block diagram showing a receiver echo measuring apparatus according to the embodiment of the invention, FIG. 5 is a waveform diagram showing the operation of the apparatus of the embodiment, FIG. 6 is a view showing a general communication system, and FIG. 7 is a speaker. FIG. 8 is a diagram for explaining the principle of echo generation, FIG. 8 is a diagram for explaining the principle of generation of a receiver echo, FIG. 9 is a schematic diagram showing a conventional transmitter echo measuring device, and FIG. FIG. 3 is a schematic diagram showing the receiver echo measuring device of FIG. 1 ... Terminal device, 2 ... 2-wire communication line, 4 ... Coupling device, 5 ... 4-wire communication line, 26 ... Transmission signal generation circuit,
29 …… Square calculation circuit, 30 …… Envelope waveform detector,
33 ... Averaging processing unit, 35 ... Transmitting signal removing unit, 37 ... Cross-correlation calculating unit, 38, 54 ... Maximum value detecting unit, 39, 56 ... Delay time detecting unit, 41, 59. Attenuation detection section, 52 ... Receiver side reference pulse generation circuit, 53 ... Unwanted waveform removal section, 55 ... Next value detection section.

Claims (2)

(57) [Claims] 1. A plurality of couplers (4a, 4b) are inserted in a 4-wire type communication line (5) formed in a closed loop, and each coupler is connected via a 2-wire type communication line (2a, 2b). Terminal device (1a, 1b)
In a speaker echo measurement device that measures the attenuation amount and delay time of the echo occurring in each of the couplers in the speech system connected to the transmitter, a sine wave signal having a voice domain frequency is used as a reference pulse signal pulse waveform. A transmission signal generating circuit (26) for applying a transmission signal amplitude-modulated by the transmission line to the transmission side two-line communication line, and the transmission signal input through the transmission side two-line communication line Waveform detecting means (30) for detecting the envelope waveform of the received voice signal, a combiner (25) for transmitting the transmitted voice signal to the two-wire communication line and receiving the transmitted voice signal, and the envelope waveform detection. A transmission signal removing means (35) for removing the transmission signal passing through the coupler (25) from the envelope waveform detected by the means, and the transmission signal is removed by the transmission signal removing means. After envelope Cross-correlation calculating means (37) for calculating a cross-correlation waveform between the waveform and the reference pulse signal waveform, and a maximum value detecting means for detecting the maximum value and the position of the cross-correlation waveform calculated by the cross-correlation calculating means. (38) and a delay time detecting means (3) for detecting a difference between the maximum value position detected by the maximum value detecting means and the reference pulse signal waveform position as an echo delay time.
9), and an attenuation amount calculating means (41) for calculating an echo attenuation amount from the amplitude of the transmission signal and the maximum value of the cross-correlation waveform.
A speaker echo measuring device having: 2. Each of the couplers in a speech communication system in which a plurality of couplers are inserted in a closed loop 4-line speech line and each terminal is connected to each coupler through a 2-wire speech line. In the receiver echo measuring apparatus that measures the attenuation amount and delay time of the echo generated in 1. at the receiving side, a transmitting signal obtained by amplitude-modulating a sine wave signal having a voice domain frequency with a pulse waveform of a reference pulse signal is transmitted from the transmitting side. A transmission signal generation circuit (26) applied to the line type speech line, and an envelope waveform detecting means for detecting an envelope waveform of the reception type signal with respect to the transmission type signal input via the reception side two-line type communication line ( 30), a pulse receiving side reference pulse generating circuit (52) for generating a reference pulse signal having the same pulse width as the reference pulse signal, and a reference pulse signal output from the receiving side reference pulse generating circuit. Cross-correlation calculating means (37) for calculating a cross-correlation waveform between the signal waveform of the above and the envelope waveform detected by the envelope waveform detecting means
And a maximum value detecting means (5) for detecting the maximum value and the position of the cross-correlation waveform calculated by the cross-correlation calculating means (5
4), a next value detecting means (55) for detecting the second largest next value of the cross-correlation waveform and its position, and echo the difference between the maximum value position and the next value position of the cross-correlation waveform. Delay time detecting means (56) for detecting the delay time,
A receiver echo measuring apparatus comprising an attenuation amount calculating means (59) for calculating an echo attenuation amount from the maximum value and the next value.