JPH05207164A - In-band signal equipment - Google Patents

Abstract

PURPOSE:To reduce nuisance noise by removing a component within the range of a frequency which is higher than the frequency of ring-back tone among quantization noise components which deteriorate call quality at the time of a calling operation. CONSTITUTION:A transmitting circuit 10 transmits at least one single frequency signal corresponding to presence or absence of a signaling signal. In a receiving circuit 20, an analog signal supplied to a terminal 7 is converted into a digital signal in an A/D converter 21. An output signal from the A/D converter 21 is supplied to a detecting circuit 22 and presence or absence of the single frequency signal is detected. The output signal from the A/D converter 21 is supplied to a digital filter 23, its single frequency signal is removed and, moreover, it is supplied to a low-pass filter 24 where the frequency of ring-back tone is removed. The outputs of the filter 23 and the output of the A/D converter 21 are changed-over in accordance with the output of the detecting circuit 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-band signal device for transmitting and receiving a required signaling signal between exchanges using an analog transmission line, and more particularly to a band for arranging a control signal such as a signaling signal in the band of a voice signal. Internal signal device.

[0002]

2. Description of the Related Art In a telephone line, especially a dedicated line using an analog transmission line, an audio signal is from 300 Hz to 3.4 KHz.
You can send and receive freely using the band range of. But,
This does not pose a problem in the case of one-to-one communication, but when a large number of one-to-N persons are targeted, an exchange is required. In addition to voice signals, various types of control signals such as dial pulses, PB signals, ringback tones, and ring tones are required between the exchanges.

These control signals required for control between the exchanges are arranged in a single frequency outside the band used by the voice signal, and transmitted / received by the presence or absence of this frequency signal, or replaced with a PCM signal. To transmit a voice signal. In a digital transmission line, transmission and reception are generally performed as a data signal other than a frame signal and a voice signal.

There is also a method of arranging the control signal within the band, as opposed to a method of arranging the control signal outside the band. Telecommunications carriers
Normally, the band required for transmitting and receiving voice signals is provided as a service, but other control signals are not provided. For this reason, we borrowed multiple lines from telecommunications carriers,
When constructing a self-employed telephone network, even if the exchange is carried in the self-employed network, so-called signaling signals such as dial pulses and PB signals which are control signals between the exchanges cannot be transmitted and received. Therefore, it is necessary to transmit and receive these signalings by using one or more single frequencies corresponding to the control signals, that is, signaling within the band to be used for the voice signal. When signaling is operated from the exchange in response to on-hook or off-hook operation of the telephone or dial pulse, the in-band signaling device performs on-hook operation of a single frequency within the voice band and transmits it to the other party. On the receiving side, the presence / absence of a single frequency is monitored by a filter, discriminated as a voice signal, received, and transmitted to the exchange as a signaling signal.

Further, the receiving circuit requires an in-band stop filter for removing the single frequency signal sent from the transmitting side. This in-band filter needs to be inserted until a call is made from the telephone, the other party answers, and then disconnected after answering. By performing the disconnecting operation, a part of a voice signal during a call becomes disconnected, and an error or the like does not occur due to a part of a data signal or the like being lost.

[0006]

In the receiving circuit of the in-band signaling device, an in-band filter for monitoring and detecting the frequency signal corresponding to the signaling signal is provided, and until the other party responds during the calling operation. An in-band stop filter inserted between is required. Conventionally, these filters have been realized with an analog filter configuration that uses a combination of coils and capacitors, but they have a large circuit scale and lack stability, so that analog signals are received at the input section of the receiving circuit. A method is conceivable in which it is converted into a digital signal and is realized by a digital filter by digital signal processing.

It is well known that quantization noise is generated by analog-to-digital conversion at the input section of the receiving circuit when it is constituted by a digital filter. Quantization noise is noise that occurs when an analog signal is input, and in the normal case, the analog signal and the quantization noise are heard at the same time, which is not a problem.
The so-called masking effect hides the quantization noise in the voice signal, so that it is not bothersome.

However, in the in-band signaling device, this quantization noise poses a problem when it is realized by a digital filter, especially during the calling operation.

That is, during the call operation, the in-band blocking filter is inserted in the receiving circuit to block the caller from hearing the single frequency corresponding to the in-band signaling signal. .. Signal components other than this frequency component pass through the receiving circuit as they are. The quantization noise generated in the analog-digital conversion circuit spreads in the pass band, and there is a problem that noise components other than the frequency components blocked by the band stop filter are perceived by the caller as they are. In a typical telephone exchange, a ringing width of 400 Hz is modulated at 16 Hz to 25 Hz, and a signal of 1 second and 2
A so-called ringback tone, which is continued by repeating the second, is transmitted from the exchange on the other side to the calling side, mixed with the in-band signal and received. Therefore, the quantization noise becomes a problem during 2 seconds when the ringback tone is cut off. At this time, the other party has not responded yet, the in-band signal and the ringback tone are mixed and received, and only the in-band signal is blocked by the in-band blocking filter. A caller listening to a ringback tone accompanied by quantization noise hears only the quantization noise when the intermittent ringback tone is interrupted, which is a path quality problem.

[0010]

An in-band signaling device of the present invention has a transmission circuit and a reception circuit, and is connected to an exchange.
A signaling signal and a voice signal among telephone signals are transmitted and received using an analog transmission line of the same band. In the transmitter circuit,
At least one single frequency signal corresponding to the presence or absence of the signaling signal is transmitted. The receiving circuit removes the single frequency signal and a signal component in a higher band than the ringback tone signal, and does not remove the input signal from which the signal component in a higher band than the single frequency signal and the ringback tone signal is removed. The input signal is switched depending on the presence or absence of the transmitted single frequency signal.

[0011]

The present invention will now be described in detail with reference to the drawings showing the embodiments of the present invention.

FIG. 3 is a block diagram of a telephone communication system including an in-band signaling device according to an embodiment of the present invention. In this telephone communication system, when a telephone call is made from the telephone 1A to the other telephone 1B, a voice signal and a control signal are sent to the in-band signaling device 3A from the exchange 2A connected to the telephone 1A. In-band signaling device 3A
Arranges the control signal in the voice signal band in the transmission circuit 10,
It is transmitted from the transmission side output terminal 6 to the reception side input terminal 7 of the partner side in-band signaling device 3B through the analog transmission path.
In the in-band signaling device 3B, in the receiving circuit 20, the voice signal and the control signal are separated and sent to the exchange 2B, and the voice signal is sent to the telephone 1B connected to the exchange 2B.

In the case of signal transmission from the telephone set 1B to the telephone set 1A, voice signals and control signals are sent from the exchange 2B connected to the telephone set 1B to the in-band signaling device 3B. In the in-band signal device 3B, the control signal is arranged in the audio signal band by the transmission circuit 10, and is transmitted from the transmission-side output terminal 6 to the reception-side input terminal 7 of the in-band signal device 3A through the analog transmission path. In the in-band signaling device 3A, in the receiving circuit 20, the voice signal and the control signal are separated and sent to the exchange 2A, and the telephone 1 connected to the exchange 2A.
A voice signal is sent to A.

Next, referring to FIG. 1, the in-band signaling device 3 (the in-band signaling device 3 of FIG. 1) according to the first embodiment of the present invention.
A and 3B) will be described.

In the in-band signal apparatus 3 according to the first embodiment of the present invention, the transmission circuit 10 is supplied to the signaling signal input terminal 5 within the band of the audio signal supplied to the transmission side input terminal 4. The signaling signal is arranged and output to the transmission side output terminal 6. The transmitter circuit 10 sends out at least one single frequency signal corresponding to the presence or absence of a signaling signal.

In the receiving circuit 20, the analog signal supplied to the receiving side input terminal 7 is converted into a digital signal in an analog / digital converter (A / D converter) 21. The digital signal from the A / D converter 21 is supplied to a detection circuit 22 having a bandpass filter for monitoring the single frequency signal, and the presence or absence of the single frequency signal is constantly detected.

The output digital signal from the A / D converter 21 is supplied to a digital filter 23 to remove a single frequency signal, and further to a low pass filter 24 for removing the frequency of the ring back tone. To be done. The low-pass filter 24 outputs only the ringback tone accompanied by the quantization noise and the ringback tone of the in-band signal and the component of the quantization noise component which is equal to or lower than the frequency of the ringback tone. A signal frequency of 400 Hz is usually used for the ring back tone, and the stop frequency of the low-pass filter 24 is also modulated in the range of 16 to 25 Hz. The output signal of the low pass filter 24 is used as a receiving path during ringing.

The received signal during the call after the response does not pass through the digital filter 23 and the low-pass filter 24, but is directly passed through the digital-analog converter (D / A converter) 26.
Is output to the output terminal 9. The detection circuit 22 detects the presence or absence of an in-band signal in the received signal, and the selection circuit 25 is controlled by the detection result to select whether the signal is calling or talking.

In the in-band signal apparatus according to the second embodiment of the present invention shown in FIG. 2, a low-pass filter is arranged on the output side of the digital-analog conversion circuit 26. That is, in the first embodiment, the low-pass filter 24 is realized by a digital filter, whereas in the second embodiment, the analog low-pass filter 24A is used. However, the characteristics and effects are similar.

[0020]

As described above, according to the present invention,
Since the low-pass filter inserted during the ringing operation is arranged in the receiving circuit of the in-band signal device, the high-frequency component higher than the frequency of the ring back tone is included in the quantization noise component that deteriorates the speech quality during the ringing operation. To be removed. As a result, annoying noise can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a telephone communication system including an in-band signaling device according to an embodiment of the present invention.

[Explanation of symbols]

 1A, 1B Telephones 2A, 2B Switchboards 3A, 3B In-band signaling device 4 Transmission side input terminal 5 Signaling input terminal 6 Transmission side output terminal 7 Reception side input terminal 8 Signaling output terminal 9 Reception side output terminal 10 Transmission circuit 20 Reception circuit 21 Analog / digital converter (A / D converter) 22 Detection circuit 23 Digital filter 24, 24A Low pass filter 25, 25A, 25B Selection circuit 26 Digital / analog converter (D / A converter)

Claims (3)

[Claims] 1. An in-band signaling device connected to an exchange to transmit and receive a signaling signal and a voice signal of a telephone signal using an analog transmission line in the same band, wherein a transmission circuit responds to the presence or absence of the signaling signal. At least one single-frequency signal is transmitted, and the receiving circuit removes the single-frequency signal and a signal component higher than the ring-back tone signal and removes a signal higher than the single-frequency signal and the ring-back tone signal. An in-band signal device for switching between an input signal from which a signal component has been removed and an input signal from which a signal component has not been removed, depending on the presence / absence of the transmitted single frequency signal. 2. The receiving circuit, an analog-to-digital converting means for converting an input analog signal sent from the transmitting circuit on the other side into a digital signal, a detecting means for detecting the presence or absence of the single frequency signal, and the digital signal. A digital filter means for removing the single frequency signal from the signal; a digital low pass filter for removing a signal component in a higher band than a ringback tone signal from the output of the digital filter means; and a detection from the detecting means. It has switching means for switching the output of the digital low-pass filter and the digital signal according to the output, and digital-analog conversion means for converting the output digital signal of the switching means into an analog signal. The in-band signal device according to claim 1. 3. The analog / digital converting means for converting the input analog signal sent from the transmitting circuit of the other side into a digital signal, the detecting means for detecting the presence or absence of the single frequency signal, and the digital signal. Digital filter means for removing the single frequency signal from the signal; first switching means for switching between the output of the digital filter means and the digital signal according to the detection output from the detecting means; A digital / analog converting means for converting the output of the switching means into an analog signal, an analog low-pass filter for removing a signal component in a higher range than a ringback tone signal from the output of the digital / analog converting means, and the detecting means. According to the detection output from the analog low-pass filter and the analog signal. And a second switching means for changing.
In-band signaling device as described.