JPS6016773B2 - two way call detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-way speech detector used in an echo control device inserted into a long-distance telephone line.

A two-way conversation detector is an echo suppressor, which is a type of echo control device, which disconnects the transmission line on the transmitting side when the receiving side is in a one-way conversation, and disconnects the transmission line on the transmitting side when the transmitting side is in a one-way conversation or when there is a simultaneous two-way conversation. Controls the echo suppression operation of connecting.

In addition, in the adaptive echo canceling device, it is an important circuit that has a control function to stop correction of the pseudo echo path during one-way communication on the transmitting side and during simultaneous two-way communication.

Conventional two-way call detection circuits compare the signal level on the transmitting side and the signal level on the receiving side, and when it is determined that the signal level on the sending side is higher, it is considered a one-way call on the sending side or a two-way simultaneous call. It was structured as follows.

However, such a configuration causes the following drawbacks. That is, '1} If the signal level on the receiving side is high and the level on the transmitting side is low, a simultaneous two-way conversation may be mistaken as a one-way conversation on the receiving side. '2' When the echo path attenuation is 4.0% and the echo path delay time is long, the echo signal level appearing on the transmission line on the transmitting side may be higher than the signal level on the receiving side, and one-way communication on the receiving side becomes a two-way communication. is incorrectly detected.

Various methods have been devised to compensate for these shortcomings.

For example, to address the drawbacks of 'li, a hysteresis or hangover time is provided to make it difficult to detect a one-way call state immediately after it is determined that the call state is one-way and one-way call state. Measures have been considered to address the drawback of '2', such as increasing the bell detection period, level averaging, and making it unaffected by the echo path delay time.
If the hangover time is too long, it will take a long time for echoes (which cannot be canceled out by an echo suppressor) to occur, and if the level detection period is set too long, the detection time of two-way communication will also be delayed, leading to call quality problems such as disconnection at the beginning of the line. This results in a decline. In the present invention, an echo path delay time detection circuit is provided to delay the reception side signal by the obtained delay time and send it to the level detection comparator that compares the transmission side signal level and the reception side signal level. The receiving side signal and the transmitting side signal are compared in a state where the side signal and its echo signal coincide in time, and the above-mentioned error, that is, an error in which a one-way communication state on the receiving side is determined to be a two-way communication state. , or errors in which a two-way communication state is determined to be a one-way communication state on the receiving side are reduced.

Furthermore, the delay time of the detection time can be shortened because it does not affect the operation. In addition, a two-way communication detector is being considered that has a configuration that detects the amount of attenuation in the echo path and causes a corresponding loss to the receiving side signal.
7-17312) If this configuration is used in combination, it is expected that errors will be further reduced. The echo path delay time can be detected by sending a reference signal to the receiving side and directly measuring it, or by correlating the signals on the transmitting side and the receiving side.

Furthermore, in the echo canceling device, the characteristics of the echo path are stored in the device as a pseudo echo path, so the echo path delay time and the amount of echo path attenuation can be easily detected. Next, a more detailed explanation will be given using the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to an echo suppression device. The echo suppression device shown in the figure is also inserted at the far end caller's side.
The receiving side signal (the near end speaker's signal) is sent from the terminal 100 through the receiving side output terminal 200 to the near end speaker. The receiving signal is sent from the transmitting input terminal 300 through the transmitting output terminal 400 to the far end speaker. The transmitting side signal also includes an echo of the receiving side signal (a signal passing through the near-end speaker's echo path), and is added to the transmitting side terminal 3001. The received signal and the transmitted signal are input to the echo path delay time detector 13, and the delay time is determined by utilizing the correlation between the two signals. The obtained delay time signal is sent to the variable delay circuit 14 to determine the delay time of the variable delay circuit 14. The received signal is delayed by the above delay time in the variable delay circuit 14 and then sent to the receiving side level detector 11.
added to. The transmitting side signal is applied to one level detector, and its output is compared with the output of the receiving side level detector by a comparator 12. When the receiving side signal is large, the transmitting side echo suppression switch 50 is activated. Comparator 1 has a signal that seems to be cut off.
Sent from 2. Although not shown in the figure, since it is best to detect the delay time detection circuit 13 during a one-way reception call, it is possible to perform reception signal detection and activate the detector 13 only when there is a reception signal, or , comparator 12
It is obvious that the detector 13 can be controlled by the output of the detector 13 to operate only during one-way communication, and to continue to hold the previous value in other cases. Figure 2 shows
This is an embodiment in which the present invention is applied to an echo canceling device. The received signal and the transmitted signal are connected in the same manner as in FIG. The transmitted speech signal containing the echo is added to the echo canceling subtracter 60 and subtracted by the amount of the pseudo echo signal sent from the pseudo echo 62.
The signal is output and sent to the transmitter output terminal 400. The pseudo echo path 62 is modified by a modification circuit 61 that correlates the received signal with the echo cancellation subtractor 60 . In order to prevent the components of the pseudo echo path 62 from being disturbed by the transmitted signal during two-way communication, a two-way communication detection circuit is required, but numbers 10 to 16
The modification is controlled to be stopped by the two-way conversation detection circuit according to the present invention. The echo parameters of the pseudo echo path 62 (for example, the impulse response in the case of a pseudo echo of the type that realizes the echo path by convolution integration) are determined by the delay time detection circuit 13 and the echo path attenuation amount detection circuit 15.
The output of the delay time detection circuit 13, that is, the delay time signal, is applied to the variable delay circuit 14, and the output of the echo path attenuation detection circuit 15, that is, the attenuation signal, is applied to the variable attenuator 1.
Added to 6. As can be easily guessed, the variable delay circuit 14 and the variable attenuator 16 constitute a simple pseudo echo path. The difference from the pseudo echo path 62 is that the phase characteristics of the true echo path are not approximated, and there is no need for urgent correction. This is because the output of the pseudo echo path consisting of 14 and 16 is only used for signal detection, and there is no need to approximate the instantaneous value of the echo signal that changes from time to time. This is because there is no need to follow temporal fluctuations in only the phase characteristics, such as the phase o. The output of the variable delay circuit 14 is applied to the level detector 11 as in FIG. 1, and the output of the level detector 11 is applied to the comparator 12. On the other hand, the signal is converted into a level signal by the transmitting signal level detector 10' and then applied to the comparator 12. The output of the comparator 12 is applied to a correction circuit 61, which controls the correction circuit to operate only when the signal on the receiver side is greater than the signal on the transmitter side. Furthermore, as is clear from their functions, the same effect can be obtained even if the variable delay circuit 14 and variable attenuator 16 are configured by replacing their positions.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of an echo suppression device according to the present invention. 100' is the receiving side input terminal, 200 is the receiving side output terminal,
300 is a transmitting side input terminal, 400 is a transmitting side output terminal, 1
3 is a delay time detection circuit, 14 is a variable delay circuit, 10 is a transmitting side level detector, 11 is a receiving side level detector, 12 is a comparator, and 50 is an echo suppression switch. FIG. 2 shows an embodiment of the echo canceling device of the present invention. 100 is the receiving side input terminal, 200 is the receiving side output terminal, 3
00 is the transmitting side input terminal, 400 is the transmitting side output terminal, 13
14 is a delay time detection circuit, 14 is a variable delay circuit, 15 is an echo attenuation amount detector, 16 is a variable attenuator, 10 is a transmitting side level detector, 11 is a receiving side level detector, 12 is a comparator, 6
1 is a correction circuit, 62 is a pseudo echo path, and 6 channels are an echo cancellation subtractor. Figure 1 Tsutomu Figure 2

Claims (1)

[Claims] 1. In an echo control device used by being inserted into a four-wire telephone line to prevent echoes occurring in a four-wire to two-wire conversion circuit, find the propagation delay time of the echo path including the four-wire to two-wire conversion circuit. a controllable variable delay circuit that gives a receiving signal a delay time corresponding to the propagation delay time; a transmitting level detector that outputs a value corresponding to the power of the transmitting signal; and the variable delay circuit. connected to the output of
The comparator includes a receiving level detector that outputs a value corresponding to the power of the receiving signal, and a comparator that receives as input the output of the transmitting level detector and the output of the receiving level detector. A two-way conversation detector characterized in that its output is a two-way conversation detection signal.