JPH06276162A - Device and method for transmitting digital voice - Google Patents

Abstract

(57) [Summary] [Purpose] A normal P
Provided are a digital voice transmission apparatus that enables a voice exchange encoded signal to be exchanged by a repeater exchange in coexistence with a CM voice signal, and a digital voice transmission method without deterioration of voice quality in exchange connection by the repeater exchange. A voice compression encoding unit 3b sets a bit steal circuit 3b ₄ for embedding a specific bit pattern in the lower 1 bit of a compression-decoded PCM signal, and sets the upper 7 bits of the PCM signal to 1 for the digital dedicated line 2 for the lower 1 bit. From a compression-encoded PCM signal generation circuit 3b ₂ for generating a PCM signal in which the encoded voice signal received from
Audio compression encoding section 3a is composed from the decoded PCM signal detecting circuit 3a _3, and the frame synchronization bit detecting circuit 3a ₄ for detecting the frame sync bits of the decoded PCM signal for detecting a specific bit pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital voice transmission apparatus for highly efficient compression coding / decoding of a PCM voice signal, and a digital voice transmission for relaying and switching a PCM voice signal and a high efficiency compression coded signal in a mixed manner. Regarding the method.

[0002]

2. Description of the Related Art When transmitting a PCM voice signal through a digital leased line, high-efficiency voice compression coding and decoding of the PCM voice signal are performed in order to effectively utilize the line capacity.

FIG. 5 is a diagram showing a switching connection configuration between digital voice transmission devices by a conventional repeater exchange. In FIG. 5, the PCM voice signal is input to the voice compression encoding unit 21b of the digital voice transmission device 21 in the station A, compression encoded, and transmitted to the digital voice transmission device 23 of the relay station through the digital leased line 22. In the digital voice transmission device 23, the compression-encoded PCM voice signal is compression-decoded by the voice compression decoding unit 23b and exchanged by the repeater exchange 24 in the state of a normal PCM voice signal (64 kb / s). If the connection destination is station B, the compressed and decrypted P
The CM voice signal is compression-encoded again by the voice compression encoder 25a in the digital voice transmitter 25 of the relay station and transmitted to the station B by the digital dedicated line 26. The PCM voice signal that has been voice compression-coded by the digital voice transmission device 27 of the B station is a voice compression decoding unit 27.
It is compression-decoded by b. Telephones 28 and 29 are directly connected to the repeater exchange 24. In FIG. 5, A
The PCM voice signal input to the station is compressed by high-efficiency voice and then transmitted through the digital leased line. In the repeater exchange, the high-efficiency voice is decoded and then exchanged. The data is transmitted and decoded at the B station with high efficiency and output as a PCM audio signal. Therefore, in the end, voice compression encoding and decoding are performed twice each for transmission between the A station and the B station.

Generally, in voice compression coding, distortion occurs in a voice waveform due to quantization noise. If the input voice signal has little noise, distortion can be tolerated, but if a voice signal to which quantization noise is added is input, the sound quality deteriorates significantly. When the connection form as shown in FIG. 5 is connected in multiple stages, the voice compression encoding and the decoding are repeated a plurality of times, so that the voice quality is greatly deteriorated.

In order to avoid this, when the PCM voice signal which has been subjected to the high-efficiency voice decoding in the voice compression decoding unit 23b in FIG. 5 is exchanged by the relay exchange 24 and connected to the voice compression decoding unit 25a, the voice compression decoding is performed. When the high-efficiency voice decoding is performed by the unit 23b, the compression-coded signal is embedded as it is in one bit of the PCM voice signal that has been voice-compressed and decoded, and the PCM voice signal is received by the voice compression-coding unit 25a. A compression coded signal embedded in 1 bit of a signal is taken out and transmitted as a compression coded signal to a digital dedicated line (hereinafter,
Described as embedding processing). FIG. 7 shows a conventional decoded PCM in which a compression coded signal is embedded by the embedding process.
The frame structure figure of a signal is shown. By performing such embedding processing in the voice compression decoding unit 23b and the voice compression encoding unit 25a which are directly connected to the relay exchange 24 of the relay station, the voice compression encoding and the decoding are performed only once.
Voice quality is not significantly impaired.

FIG. 6 is a block diagram showing the configuration of a conventional digital voice transmission device which enables such embedding processing.

In FIG. 6, digital voice transmission devices 23 and 25 exchange-connected by a repeater exchange 24.
Is composed of a voice compression encoding unit 23a, a voice compression decoding unit 23b, a voice compression encoding unit 25a and a voice compression decoding unit 25b, respectively.

The voice compression / decoding unit 23b and the voice compression / decompression unit
The encoding unit 25b is a voice compression / decoding circuit 23b.₁,bit
Steel circuit 23b₂, And the changeover switch 23b₃And sound
Voice compression / decoding circuit 25b₁, Bit steal circuit 25
b₂, And the changeover switch 25b ₃Composed of.

Audio compression coding unit 23a and audio compression code
The encoding unit 25a is a voice compression encoding circuit 23a.₁, PCM
Signal lower 1-bit extraction circuit 23a₂, And switch
Switch 23a₃And audio compression encoding circuit 25a₁, PCM communication
No. lower 1-bit extraction circuit 25a ₂, And mode switching switch
Switch 25a₃Composed of.

Next, the operation of the conventional digital voice transmission device will be described with reference to FIGS. When the digital voice transmission device 23 and the digital transmission device 25 are connected by the exchange processing by the repeater exchange 24, A
When a voice compression coded signal is input from the digital voice transmission device 21 of the station to the voice compression decoding section 23b of the relay station through the digital leased line 22, the repeater exchange 24 uses the call connection information to send the digital signal via the digital leased line 22. When it is detected that the call has passed through the voice transmission device 23 and the destination of the call is beyond the digital leased line 26 via the digital voice transmission device 25, the mode changeover switches 23a ₃ and 23b _{3 are} generated by the changeover signal P. Of the mode changeover switches 25a ₃ and 25b ₃ to the b side by the switching signal Q.

The voice compression coded signal inputted from the digital leased line 22 is inputted to both the voice compression decoding circuit 23b ₁ and the bit steal circuit 23b ₂ , but since the mode changeover switch 23b ₃ is on the side b. The output of the bit steal circuit 23b ₂ is transmitted to the transit exchange 24. As shown in FIG. 7, in the bit steal circuit 23b ₂ , the voice compression / decoding signal (64 kb / s) from the voice compression / decoding circuit 23b ₁ is input and the lower 1 bit thereof is compressed by the digital dedicated line 22. A process of embedding the encoded signal (8 kb / s) as it is is performed. A signal in which a voice compression coded signal (8 kb / s) is embedded in the lower 1 bit is a compression decoded PCM signal (64 kb / s).
As a result, it is exchanged by the repeater exchange 24 and input to the voice compression encoding unit 25a of the digital voice transmission device 25. The compression-decoded PCM signal is a voice compression encoding circuit 2
5a ₁ and the PCM signal lower 1-bit extraction circuit 25a ₂ . The PCM signal lower 1 bit extracting circuit 25a ₂ extracts and outputs the voice compression coded signal (8 kb / s) embedded in the lower 1 bit of the compression-decoded PCM signal on the digital voice transmission device 23 side. Since the mode changeover switch 25b ₃ is connected to the b side, the voice compression coded signal is transmitted to the digital voice transmission device 27 of the B station by the digital leased line 26. On the other hand, when the telephone 28 or the telephone 29 is connected to the digital voice transmission device 23 or the digital voice transmission device 25 by the exchange processing by the relay exchange 24, the relay exchange 24 does not connect to the digital voice transmission device 23. The mode changeover switches 23a ₃ and 2 by the changeover signal P.
3b ₃ is switched to the a side, and the mode changeover switch 25a ₃
And return to the a side of 25b ₃ .

In this state, the voice compression coded signal input from the digital dedicated line 22 is the voice compression decoding circuit 23.
Input to both b ₁ and bit steal circuit 23b ₂ .
The voice compression / decoding signal from the voice compression / decoding circuit 23b ₁ is transmitted to the telephone 28 or the telephone 29. On the other hand, the PCM voice signal from the telephone 28 or the telephone 29 is compressed by the voice compression encoding circuit 23a ₁ of the voice compression encoding unit 23a of the digital voice transmission device 23 or the voice compression encoding unit 25a of the digital voice transmission device 25. The audio signal is compression-encoded in the encoding circuit 25a ₁ and then the digital dedicated line 22 or the digital dedicated line 26
Sent to.

In this way, even in the conventional digital voice transmission apparatus, the voice compression coded signal on the digital leased line can be switched and connected without increasing the distortion of the voice waveform due to the quantization noise.

[0014]

However, in the case of the conventional example, the embedding process is performed when the digital voice transmission devices are exchange-connected by the control of the switching signal from the repeater exchange, and the normal PCM voice signal is transmitted. This is not performed when a communication device (for example, a telephone) for inputting / outputting is exchange-connected to the digital voice transmitting device.

Therefore, not only the digital voice transmission device for transmitting and receiving the compression coded signal through the digital leased line but also the communication device (for example, telephone) for inputting and outputting the normal PCM voice signal are mixed and connected to the repeater exchange. If it exists, it is judged for each call connection whether it is a switching connection between digital voice transmission devices or a communication connection for inputting / outputting a normal PCM voice signal to / from the digital voice transmission device, and the relay exchange side determines The embedding processing operation must be controlled by the switching signal of.

However, since an ordinary transit exchange generally does not have a function of transmitting a control signal for controlling the embedding process according to the call connection information as described above, unless the above-mentioned function is added to the transit exchange, There is a problem that such a switching connection form cannot be dealt with.

The present invention is to solve such a conventional problem, and it is possible to determine whether or not the connection partner is the digital voice transmission device even if there is no control signal from the repeater exchange in the digital voice transmission device. Recognizing by itself, in the case of exchange connection of digital voice transmission devices, the compression encoded signal from the digital leased line is exchanged without compression and decoding, and voice compression and decoding at the time of exchange in the repeater exchange It is an object of the present invention to provide a digital voice transmission device and a digital voice transmission method that reduce the deterioration of voice quality by eliminating the need for encoding.

[0018]

In order to achieve the above object, in a digital voice transmission apparatus of the present invention, a voice compression / decoding section stores a compression-decoded PCM signal in a lower bit of a compression-decoded PCM signal. Bit stealing means for embedding the indicated bit and all upper bits of the PCM signal are 1
And an encoded PCM signal generating means for generating a PCM signal in which the received encoded audio signal is embedded in the lower bits,
Output PCM signal from bit steal means and encoded PC
The PCM signal output from the M signal generating means is composed of a mode switching means for switching the output PCM signal by a switching signal from the voice encoding section transmitting in the opposite direction on the same channel.

Further, the voice compression encoding unit detects that a bit indicating that it is a compressed and decoded PCM signal is embedded in the lower 1 bit of the received PCM signal, and transmission in the opposite direction on the same channel is performed. Compression / decoding PCM detection means for sending a switching signal to the speech compression / decoding device performing the above, and for the encoded speech signal embedded that the encoded speech signal is embedded in the lower 1 bit of the received PCM signal. Frame synchronization bit detecting means for detecting by the frame synchronization bit, transmitting a switching signal to the mode switching means in the device, and further transmitting the switching signal to the audio compression decoding unit performing reverse transmission on the same channel; , The switching signal from the frame synchronization bit detecting means switches between the encoded audio signal and the signal obtained by extracting the lower 1 bit of the received PCM. It consists of mode switching means to be.

When the digital voice transmission device composed of the voice compression / decoding unit and the voice encoding unit is connected to another digital voice transmission device or a communication device for inputting / outputting a normal PCM voice signal by an exchange. In the digital voice transmission method of No. 1, it is identified whether or not the connection partner is the digital voice transmission device, and when it is the digital voice transmission device, the compression coded signal is embedded in the lower 1 bit of the PCM voice signal. It is characterized in that after the processing, the exchange processing is performed, and after the exchange processing, the voice compression coded signal embedded in the lower 1 bit of the PCM voice signal is extracted and transmitted to the digital voice transmission device of the connection partner.

[0021]

With such a configuration, the digital voice transmission apparatus of the present invention determines whether the connection partner is a digital voice transmission apparatus including the same voice compression encoding unit and voice compression decoding unit. It can be recognized even in the absence of a control signal from the transit exchange. Therefore, if the connection partner is the same digital voice transmission device without depending on an external device such as a repeater switch, it is possible to perform a switching connection without compressing and decoding the compression encoded signal from the digital leased line. become.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital voice transmission device and a digital voice transmission method according to an embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a switching connection configuration between digital voice transmission devices by a relay switch according to an embodiment of the present invention. In FIG. 1, the PCM voice signal is input to the voice compression encoding unit 1a of the digital voice transmission device 1 in the station A, compression-encoded, and transmitted to the digital voice transmission device 3 of the relay station through the digital leased line 2. In the digital voice transmission device 3, the compression-encoded PCM voice signal is compression-decoded by the voice compression / decoding unit 3b, and a normal PC is used.
It is exchanged by the repeater exchange 4 in the state of M voice signal (64 kb / s). If the connection destination is station B, the compressed and decoded PCM voice signal is transmitted to the digital voice transmission device 5 of the relay station.
In this case, it is compressed and encoded again by the voice compression encoding unit 5a and transmitted to the digital voice transmission device 7 of the B station by the digital leased line 6. Telephones 8 and 9 are connected to the repeater exchange 4.

FIG. 2 is a block diagram showing the configuration of a digital voice transmission device according to an embodiment of the present invention. In a digital leased line, a voice compression coded signal is usually multi-channel multiplexed and transmitted, so a digital voice transmission apparatus requires a multiplexing and demultiplexing unit.
Since only one channel is dealt with in FIGS. 1 and 2, it is omitted.

In FIG. 2, the digital voice transmission devices 3 and 5 exchange-connected by the repeater exchange 4 respectively include a voice compression encoding unit 3a, a voice compression decoding unit 3b, a voice compression encoding unit 5a, and a voice compression decoding unit. It is composed of the section 5b.

The voice compression / decoding unit 3b and the voice compression / decoding unit 5b respectively include a voice compression / decoding circuit 3b ₁ , a compression / encoded PCM signal generation circuit 3b ₂ , a decoding notification bit pattern circuit 3b ₃ , and a bit steal circuit 3b. ₄ , a changeover switch 3b ₅ , a voice compression decoding circuit 5b ₁ , a compression coding PCM signal generation circuit 5b ₂ , a decoding notification bit pattern circuit 5b ₃ , a bit steal circuit 5b ₄ and a changeover switch 5b _5. .

The voice compression encoding unit 3a and the voice compression encoding unit 5a include a voice compression encoding circuit 3a ₁ , a PCM signal lower 1 bit extraction circuit 3a ₂ , a decoded PCM signal detection circuit 3a ₃ , and a frame synchronization bit detection circuit. 3a _4, oR gates 3a _5, and changeover switches 3a ₆ and audio compression encoding circuit 5a _1, PCM signal low-order bit extraction circuit 5a _2, decoded PCM signal detecting circuit 5a _3, the frame sync bit detection circuit 5a _4, oR It is composed of a gate 5a ₅ and a changeover switch 5a ₆ .

Next, the operation of the digital voice transmission apparatus according to the embodiment of the present invention will be described with reference to FIGS.

FIG. 2 shows the configuration of one channel of the digital voice transmission devices 3 and 5 at the relay station.
The voice signal is sampled at 8 kHz and encoded at 8 bits to have a transmission rate of 64 kb / s, while the voice compression encoded signal has a transmission rate of 8 kb / s including a frame synchronization bit. The transmission speed of the transmission line 2 and the transmission line 6 is 8 kb /
s, the transmission speed between the digital voice transmission device and the repeater exchange is 64 kb / s. In FIG. 2, when a voice compression coded signal is input to the voice compression decoding unit 3b of the digital voice transmission device 3 from the digital leased line 2, it becomes a voice compression decoding PCM voice signal and is input to the bit steal circuit 3b ₄ . The bit steal circuit 3b ₄ obtains the decoding notification bit indicating that the decoding has been performed by the decoding notification bit pattern circuit 3b ₃ and embeds it in the lower 1 bit of the compression-decoded PCM signal and outputs it.

FIG. 3 shows a frame structure diagram of the compression-decoded PCM signal from the bit steal circuit.

When the digital voice transmission device 3 and the digital voice transmission device 5 are connected by the repeater exchange 4, the voice compression encoding unit 5a of the digital voice transmission device 5 is connected.
Then, when the compressed and decoded PCM signal in which the decoding notification bit is embedded in the lower 1 bit is input, only the lower 1 bit is extracted by the PCM signal lower 1 bit extraction circuit 5a ₂ and decoded by the decoded PCM signal detection circuit 5a ₃ . When the encryption notification bit is determined, the switching signal Q is sent to the voice compression decoding unit 5b which is transmitting in the opposite direction on the same channel via the OR gate 5a ₅ .

In the voice compression / decoding unit 5b, first, similarly to the voice compression / decoding unit 3b, the first changeover switch 5b ₅ is set to a.
Although the side is set, the changeover switch 5a ₅ is set to the b side by the switching signal Q from the voice compression encoding unit 5a, and the output of the compression / decoding PCM signal generation circuit 5b ₂ is the voice compression of the digital voice transmission device 3. It will be transmitted to the encoding unit 3a.

FIG. 4 shows a compression-encoded PCM signal generation circuit 5b.
₂ shows a frame configuration diagram of a compression-encoded PCM signal output by the _second embodiment. In this way, the compression-encoded PCM signal generation circuit 5b
₂ designates all the upper 7 bits of the PCM audio signal as 1, and transmits the encoded PCM signal having a structure in which the compression encoded signal from the digital dedicated line 6 is embedded in the lower 1 bit. There is a frame synchronization bit in the compression coded signal in the lower 1 bit, which is the digital transmission device 7 of station B.
It is added by the voice compression encoding unit 7a.
Except for the above-mentioned synchronization bit, it is a compression coded audio signal.

In the voice compression encoding unit 3a of the digital voice transmission device 3 which receives the compression encoded PCM signal, the PC
The lower 1 bit of the compression-encoded PCM signal is extracted by the M signal lower 1-bit extraction circuit 3a ₂ and the synchronization bit of the compression-encoded signal is detected by the frame synchronization bit detection circuit 3a _4. When it is determined that the switch is embedded, the switching signal P is sent to the audio compression decoding unit 3b via the OR gate 3a ₅ . The switching signal P has already been output by the decoding PCM signal detection circuit 3a ₃ .
Even when the PCM signal is transmitted, the decoded PCM signal detection circuit 3
Since the decoded PCM signal may switch to the compression coded PCM signal before a ₃ detects the decoding notification bit, the output of the frame synchronization bit detection circuit 3a ₄ and the coded PCM signal detection circuit 3a ₃ The output of the output OR gate 3a ₅ is used as the switching signal P. The frame synchronization bit detection circuit 3a ₄ also sends a switching signal to the changeover switch 3b ₆ . By this switching signal, the changeover switch 3b ₆ is switched to the b side, and the voice compression coded signal from the PCM signal lower 1-bit extraction circuit 3a ₂ is sent to the digital leased line 2.

In the voice compression / decoding unit 3b, the changeover switch 3b ₅ is switched by the changeover signal P from the voice compression / encoding unit 3a.
Is switched to the b side, and the output of the compression-encoded PCM signal generation circuit 3b ₂ is sent to the repeater exchange 4 as in the voice compression decoding unit 5b. Compression-encoded PCM signal generation circuit 3b ₂
As shown in FIG. 4, the upper 7 bits are all set to 1, and the voice compression coded signal (8 kb) from the digital leased line 2 is set.
/ S) is embedded in the lower 1 bit and a compression-encoded PCM signal (64 kb / s) having a frame structure is transmitted. Bottom 1
A frame synchronization bit exists in the voice compression coded signal in bits, which is added by the voice compression coding unit 1a of the digital voice transmission apparatus 1 of the A station.

The compression-encoded PC is transmitted via the repeater exchange 4.
In the voice compression encoding unit 5a of the digital voice transmission device 5 that has received the M signal, the lower 1 bit of the compression encoded PCM signal is extracted by the lower 1 bit extraction circuit 5a ₂ and the frame synchronization bit detection circuit 5a ₄ When it is determined that the voice compression coded signal is embedded by detecting the frame synchronization bit of the voice compression coded signal,
Changeover switch 5a _{6 is changed} to b side, and compression coding PC
The audio compression coded signal (8 kb / s) extracted from the lower 1 bit of the M signal is sent to the transmission line 6. The switching signal Q is also sent to the voice compression / decoding unit 5b through the OR gate 5a ₅ .

For the voice compression / decoding unit 5b, the changeover switch 5b has already been switched to the b side by the output from the decoded PCM signal detection circuit 5a ₃ .

By the above processing procedure, the voice compression coded signal (8 kb / s) sent from the digital leased line 2 is sent.
s) is embedded in the decoded PCM signal (64 kb / s) by the voice compression decoding unit 3a, is transmitted to the digital voice transmission device 5 via the repeater exchange 4, and the voice compression encoding unit 5a which has received this signal. Takes out the audio compression coded signal embedded in the decoded PCM signal and sends it to the transmission line 6.

The voice compression coded signal from the transmission line 6 is also sent to the transmission line 3 in the same manner. In the digital voice transmission device connected to the repeater exchange, the exchange process of the voice compression encoded signal can be performed without performing voice encoding / decoding.

It should be noted that the voice compression coding unit 5 uses the decoded PCM.
As a result of receiving the signal, the decoded PCM signal detection circuit 5a ₃ detects the decoding notification bit from the decoded PCM signal, the changeover switch 5b ₅ switches to the b side, and thus far the decoded PCM from the bit steal circuit 5b ₄ PC decoding signal
The switching signal of the M signal detection circuit 3a ₃ is a compression coded PCM.
When switching to the coded PCM signal from the signal generation circuit 5b ₂ is switched, the frame synchronization bit detection circuit 3a ₄ detects the frame synchronization bit and sends the switching signal P. The changeover switch 3b ₅ does not return to the side a. .

When the call is terminated and the call exchange between the digital voice transmission devices 3 and 5 is cut off by the repeater exchange 4,
Frame sync bit detection circuit 5 of the audio compression coding unit 5a
a ₄ or the frame synchronization bit detection circuit 3a ₄ of the voice compression encoding unit 3a does not detect the frame synchronization bit, and the changeover switch 5a _{6 of} the voice compression encoding unit 5a,
The changeover switch 5b _{5 of} the voice compression decoding unit 5b ₅ , the changeover switch 3a _{6 of the} voice compression encoding unit 3a, and the changeover switch 3b ₅ of the voice compression decoding unit 3b all return to the side a.

Next, the case where the digital voice transmission device 3 is exchange-connected to the telephone 8 or the telephone 9 by the repeater exchange 4 will be described. In this case, when the voice compression coded signal is input from the digital dedicated line 2 to the voice compression decoding unit 3a of the digital voice transmission device 3, the voice compression decoding circuit 3b ₁ compresses and decodes the bit compression circuit 3b.
Since the decoding notification bit pattern is embedded in the lower 1 bit by b ₄ and the changeover switch 3b ₅ is initially set to the a side, the decoding P in which the decoding notification bit is embedded is set.
The CM signal is converted into an analog voice signal as it is and sent to the telephone. In this case, as shown in FIG. 3, the decoding notification bit is regularly embedded in the lower 1 bit, so that the voice quality is hardly deteriorated even when connected to the telephone.

When the telephone 8 or the telephone 9 is exchange-connected to the repeater exchange 4, when the analog voice signal from the telephone is converted into a normal PCM voice signal in the repeater exchange 4 and input to the digital voice transmitting device 5, Although the compression-encoded input to the audio compression encoding circuit 5a _1, selector switch 5a ₆ is sent directly to the digital leased line 6 because it is initially set to a side. The PCM audio signal is also input to the PCM signal lower 1 bit extraction circuit 5a ₂ , but since the predetermined decoding notification bit pattern and the frame synchronization bit are not set, the changeover signal does not change and the changeover switches 5a ₅ and 5a are not changed. ₆ retains the state on the a side.

Further, the fact that the compression coded signal is embedded in the lower 1 bit of the coded PCM signal is performed by detecting the frame sync bit of the compression coded signal by the frame sync detection circuit 5a ₄ . As another method, a special bit pattern indicating that the compression-coded signal is embedded in the lower 1 bit is embedded in the lower 2 bits of the PCM signal, and the bit pattern is detected instead of the frame synchronization detection circuit. It may be realized by providing a circuit.

[0045]

As is apparent from the above description, in the digital voice transmission apparatus of the present invention, when the voice compression encoded signal is transmitted through the digital leased line and is exchange-connected by the repeater exchange, the voice encoding / decoding is performed. Since it is not necessary to perform duplication, and it is possible to uniquely recognize inside the device that the other party of the exchange connection by the relay exchange is the digital voice transmission circuit having the same voice compression encoding and voice compression decoding processing function, A control signal from an external device such as a repeater exchange is not particularly required.

Therefore, even if other normal PCM signal transmission lines are mixed in the exchange connection by the repeater exchange, it is not necessary to provide a control function for identifying the connection partner in the repeater exchange, and the digital voice can be selected without selecting the repeater exchange. A transmission system can be constructed, and PCM can be used during exchange connection.
It is possible to reduce the sound quality deterioration due to the voice compression encoding process.

[Brief description of drawings]

FIG. 1 is a diagram of an exchange connection configuration between digital voice transmission devices by a relay exchange according to an embodiment of the present invention.

FIG. 2 is a configuration block diagram of a digital voice transmission device in the above embodiment.

FIG. 3 is a frame configuration diagram of a compression-decoded PCM signal.

FIG. 4 is a frame configuration diagram of a compression-encoded PCM signal.

FIG. 5 is a diagram of a switching connection configuration between digital voice transmission devices by a conventional relay exchange.

FIG. 6 is a configuration block diagram of a conventional digital voice transmission device.

FIG. 7 is a frame configuration diagram of a conventional decoded PCM signal.

[Explanation of symbols]

1, 3, 5, 7 Digital voice transmission device 1a, 3a, 5a, 7a Voice compression coding unit 1b, 3b, 5b, 7b Voice compression decoding unit 2, 6 Digital dedicated line 3a ₁ , 5a ₁ Voice compression coding Circuits 3a ₂ , 5a ₂ PCM signal lower 1-bit extraction circuit 3a ₃ , 5a ₃ Decoded PCM signal detection circuit 3a ₄ , 5a ₄ Frame synchronization bit detection circuit 3a ₅ , 5a ₅ OR gate 3a ₆ , 5a ₆ Mode change switch 3b ₁ , 3b ₁ voice compression / decoding circuit 3b ₂ , 3b ₂ compression coding PCM signal generation circuit 3b ₃ , 3b ₃ decoding notification bit pattern circuit 3b ₄ , 3b ₄ bit steal circuit 3b ₅ , 3b ₅ mode selector switch

Claims (2)

[Claims] 1. A digital voice transmission apparatus comprising a voice compression encoding unit and a voice compression decoding unit, for transmitting and receiving voice compression encoded signals to and from each other via a digital leased line, wherein the voice compression decoding unit is compression decoding. Bit stealing means for embedding a bit indicating a compressed and decoded PCM signal in the lower bits of the PCM signal, and a PCM signal in which the upper bits of the PCM signal are all 1s and the received encoded audio signal is embedded in the lower bits. Coded PCM signal generating means for generating, output PCM signal from bit stealing means and coded PC
And a mode switching means for switching the output PCM signal of the M signal generation means by a switching signal from the voice encoding section transmitting in the opposite direction on the same channel, and the voice compression encoding section is provided for the received PCM signal. A compression that detects that a bit indicating that it is a compressed and decoded PCM signal is embedded in the lower 1 bit and sends a switching signal to the audio compression and decoding unit that is transmitting in the opposite direction on the same channel. The decoding PCM detecting means and the fact that the encoded voice signal is embedded in the lower 1 bit of the received PCM signal is detected by the frame synchronization bit of the embedded encoded voice, and the switching signal is sent to the mode switching means in the device. And a frame synchronization bit detecting means for transmitting a switching signal to a voice decoding unit which is transmitting in the opposite direction on the same channel. A digital voice transmission apparatus comprising: a mode switching unit for switching between a coded voice signal and a signal obtained by extracting the lower 1 bit of the received PCM in response to a switching signal from the frame synchronization bit detection unit. . 2. The digital voice transmission device composed of the voice compression decoding unit and the voice encoding unit is connected to another digital voice transmission device or a communication device for inputting / outputting a normal PCM voice signal by a switch. In the case of the digital voice transmission method, it is discriminated whether or not the connection partner is the digital voice transmission device, and if it is the digital voice transmission device, the compression coded signal is the lower 1 bit of the PCM voice signal. Is embedded, the exchange process is performed, and after the exchange process, the lower order 1 of the PCM audio signal
A digital voice transmission method comprising extracting a voice compression coded signal embedded in bits and transmitting it to a digital voice transmission device of a connection partner.