JPS5853537B2 - Time-division channel interruption method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time-division call path interrupting system that connects a call path in use with another call path in a time-division switch to enable interrupt calls.

Conventionally, in space-division type exchanges, interrupting calls have been carried out by doubly connecting the interrupting side's communication path to an appropriate position of the interrupted side's communication path, depending on the switching system.

In this method, the interrupted side communication path and the interrupting side communication path are physically connected in parallel, so the speech quality on these communication paths inevitably deteriorates, but this is not necessarily fatal. It was so strange that it did not cause any practical problems.

However, in a time division switch, for example, a voice analog signal from a subscriber line is converted into a digital signal, and the digital code is exchanged in a time division manner.

Digital signals, unlike analog signals, require separate signal paths (communication paths) for going and returning.

Therefore, the time division switch is necessarily a 4-wire switch, and the analog/digital conversion point has a 2-wire/4-wire switch.
Requires a 4-wire conversion circuit (hybrid circuit).

The 2-wire/4-wire conversion circuit makes the impedance of the balanced wiring network equal to the impedance of the 2-wire line, thereby increasing echo path loss, preventing noise generation in the 4-wire line, and ensuring stable operation. Guaranteed passage.

In other words, in a time-division switch, as in a conventional space-division switch, in the analog (two-wire) line part,
If a double connection is made for an interrupt call, the impedance seen from the 2-wire/4-wire conversion circuit to the 2-wire line side will change, the balance in the 2-wire/4-wire conversion circuit will be disrupted, and stable calls will no longer be guaranteed. .

Further, in a time-division communication path where digital audio signals are transmitted, it is not possible to realize an interrupt call based on the concept of a simple double connection, as in the case of an analog line.

On the other hand, due to its nature, time-division switching equipment for subscriber ladders must be equipped with a call waiting function, but the switching equipment itself has not yet reached the level of practical use, so No method has been found to include this.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to provide an economical time-division call path interruption method that guarantees call quality during interrupted calls in a time-division exchange and utilizes the basic functions of the time-division exchange. The aim is to provide something new.

A feature of the present invention is that in a time-division exchange, the time-division call path switch is provided with an audio mixing means, the interrupted-side communication path and the interrupted-side communication path are connected to this, and the respective call voices are digitally mixed. This is a time-division channel interruption method that realizes interruption calls by doing so.

Hereinafter, detailed questions will be asked regarding embodiments of the present invention according to the drawings.

FIG. 1 is a relay system diagram of one embodiment of the time-division channel interruption method according to the present invention, and FIG. 2 is a relay system diagram of another embodiment.
FIG. 3 is a relay system diagram of another embodiment, and FIG. 4 is a diagram of the principle of voice mixing using a voice mixing means, for example, a voice mixing trunk in the time-division channel interruption system according to the present invention. FIG. 5 is a block diagram of one embodiment of the audio mixing circuit in the audio mixing trunk, and FIG. 6 is a block diagram of another embodiment of the audio mixing circuit.

Here, 1.2 is a subscriber telephone during a call, 3a is a space-division type concentrating ladder switch, 3b is a time-division type concentrating ladder switch, and 4 is a distribution ladder switch, each of which is connected to the call path network. It constitutes.

5 is a call trunk (TRK), 6 is an interrupt trunk (
ICT-NT), 1 is the analog-digital conversion point (
F), 8 is mixed voice trunk (MIX TRK),
9 is an interrupt tone source (T); 10 is a subscriber trunk (
SUBT), 11 is the subscriber telephone (A, B) before interruption
The communication path between 1 and 2, 12 is the subscriber telephone after 2 interrupts (4
) and the voice mixing trunk 8; 13 is the communication path between the subscriber telephone [F]) 2 after the interruption and the voice mixing trunk 8; 14 is the communication path between the interrupt circuit C and the voice mixing trunk after the interruption. Trunk 8
15 is a communication path between the interrupt tone source (1) 9 after interruption and the audio mixing trunk 8; 16 is a mixing circuit in the audio mixing trunk 8; together with the communication path network, This constitutes a time-division channel interruption system according to the present invention.

Further, 17 is a serial/parallel conversion circuit, 18 is an expander, 19
is an adder, 20 is a subtracter, 21 is a compressor, 22 is a parallel-to-serial conversion circuit, 23 is a 1/3 circuit, which constitutes the mixing circuit 16, and 24.25 is a , are an incoming digital highway and an outgoing digital highway connected to the mixing circuit 16, respectively.

First, referring to FIG. 1, a relay system of an embodiment of the time-division channel interrupt system according to the present invention will be described.

The subscriber telephones (A, B) 1.2 are connected by a space division type concentrating ladder switch 3a, a subscriber trunk 10, a call path 11 in a time division type distribution ladder switch 4, and a call trunk 5, and are in the middle of a call. Suppose that the state is as follows.

After passing through the subscriber trunk 10, the analog voice signal from the subscriber telephone (A) 1 is converted from analog to digital at a point 7, and after being exchanged at the distribution ladder switch 4,
It is sent via the call trunk 5 to the subscriber's telephone set 2).

At this time, when an interrupt request is generated from the interrupt line C, the communication line 11 connecting the subscriber telephones (A, B) 1.
and set up communication paths 12, 13, 14, 15, respectively, to the subscriber telephone (4) 1 via the subscriber trunk 1o and to the subscriber telephone (B) via the communication trunk 5.
2. Connect interrupt line C1 interrupt tone source 9 to voice mixing trunk 8 via interrupt trunk 6.

Since the switching time of the communication path in the distribution ladder switch 4 is extremely short (several μs or less), the time required for this connection change is such that it practically does not affect the communication at all.

In this way, digital voice signals originating from the subscriber telephones (A, B) 1, 2, the interrupt line C and the interrupt tone source 9 are routed through the communication paths 12, 13.14° 15 to the voice mixing trunk 8. and digitally mixed.

Next, in the opposite direction of each communication path 12, 13, 14, 15, the mixed voice from which the own voice has been removed is sent back, so that the subscriber telephones (A, B) 1.2 and the interrupt line C
can receive the voices and interrupt tones of the other two parties, respectively.

In other words, an interrupt call state can be established.

In addition, in the case of a time division switch, the communication path is as described above.
There is a forward communication and a return communication, and separate communication channels (time-division digital transmission channels) are used in Bird's view, but in Fig. 1,
This is omitted and the forward and backward directions are expressed together as a single line.

This also applies to FIGS. 2 and 3, which will be explained below.

Further, the interrupt tone source 9 may supply the interrupt tone for a certain period of time at the beginning of the interrupt call, for the entire period during the interrupt call, or may not supply the interrupt tone at all, depending on the need. can.

This also applies to the embodiments shown in FIGS. 2 and 3 described below.

Furthermore, in the embodiment shown in FIG. 1, the subscriber trunk 10 is inserted in the post-concentration position of the space-division type concentrator switch 3a, but if necessary, the subscriber trunk 10 can be inserted into the space-division type concentrator switch 3a. The above-mentioned, ie, subscriber line side, may be inserted correspondingly or commonly to the subscriber line.

The basic functions of the subscriber trunk 10 include supplying call current to the subscriber, monitoring calls, scanning dial pulse signals, off-hook/on-hook dial pulse information, etc., and transmitting/receiving analog call audio to/from the analog/digital conversion point 7. etc.

Next, in another embodiment shown in FIG. 2, the concentration ladder is a time division type concentration ladder switch 3b, and the subscriber trunk
Due to its nature, 0 is necessarily inserted at a position before convergence, and it performs the same function as in FIG. 1.

Furthermore, in another embodiment shown in FIG. 3, the configuration of the entire time-division channel switch (communication channel network) is the same as that in FIG. It is only accommodated in the staircase switch 3b, and the interrupt call function is the same as the embodiment shown in FIG. 1 or 2.

Next, the principle of audio mixing in the audio mixing trunk 8 will be explained with reference to FIG.

In FIG. 4, a mixing circuit (M
IX) 16 digitally performs audio mixing for interrupt calls, and other general functional parts are omitted from illustration as an audio mixing trunk 8.

The digital voice signals from the subscriber telephones (A, B) 1, 2, the interrupt circuit C and the interrupt tone source (T) 9 are respectively denoted a, E)*Ced, and in the figure:
It is fed into the mixing circuit 16 in the voice mixing trunk 8 via the distribution ladder switch 4 or the time-sharing concentrator ladder switch 3b along the connection path indicated by the arrow.

The mixing circuit 16 receives these digital audio signals a, b,
c, d are mixed digitally and subscriber telephones (A, B
)1.2 and interrupt line C, except for their own digital audio signals a, b, c;
+c+d, for B, a+c+d, for C,
A digital audio signal of the form a-4-b+d is transmitted.

This results in A and B. A three-party call by C, that is, an interrupt call becomes possible.

Note that the reverse path to the interrupt tone source (1) 9 includes:
As shown in FIG. 4, an audio signal in the form of a + b + c may be returned, or may not be returned at all;
It is clear that the present invention is not limited to any form of return.

In the embodiments shown in FIGS. 1, 2, and 3, the 2-wire and 4-wire conversion circuits are located at the analog-to-digital conversion points (6) and 7, respectively, and the mixing and distribution of audio is carried out at the audio mixing trunk. Since this is done digitally at the logic level within 8, problems such as impedance unbalance for each line can be solved.
This guarantees stable interruption calls.

Finally, regarding the embodiment of the audio mixing circuit according to the present invention,
Ask detailed questions according to Figures 5 and 6.

In FIG. 5, digital audio signals a and b.

c and d are input in series from the incoming digital highway 24 (they do not necessarily have to be continuous).

). These are converted into a parallel signal format by a serial/parallel conversion circuit (SP) 1γ.

These signals are generally in PCM (Pulse Code Modulation) companded code format and therefore cannot be added directly.

Therefore, it is linearized by an expander (EXP) 18 (for example, converting an 8-bit companded code into a 16-bit linear code).

). These converted linearized digital audio signal codes a', b', c', and d' are input to an adder (ADD) 19 and added.

The addition result is a'+b'+d'.

This is further subtracted by a subtracter 20.

That is, corresponding to input signal a, V+♂+d', corresponding to input signal S, a'+c'+a', input signal C
Corresponding to the input signal d, it becomes l+b'+d', and corresponding to the input signal d, it becomes a'+b'+c'.

These correspond to what should be sent back to each line as digital audio signals, but since they have been linearized, they need to be converted back to a companded code (for example, converting 16 straight bits to 8 bits of companding).

). Therefore, these are passed through a compressor (COM) 21 and audio signals b + c + d, a + c +
d, a + b + d.

Get a + b + c.

These are serialized by a parallel-to-serial converter (ps) 22 and sent to the exit highway 25.

The outgoing highway 25 is paired with the incoming highway 24, forming a round-trip audio signal path.

In the above question, for example, since the output is simply added b + c + d to the input a, the audio level may be too high and reduce the stability of the line.

Therefore, as a countermeasure to this, depending on the input level,
There may be cases where it is necessary to control the output level to an appropriate value.

As a countermeasure for this, Figure 6 shows that the sum of the levels for the three parties is
This shows an embodiment of the audio mixing circuit 16 which reduces the noise to /3.

Here, a 1/3 reduction circuit 23 is inserted between the subtracter 20 and the compressor 21 to optimize the output audio level.

The rest is exactly the same as that shown in FIG.

As discussed in detail above, according to the present invention, by providing a relatively simple voice mixed trunk in a time division switch, and by utilizing the connection switching function that the time division switch originally has, The effect of this invention is that it is possible to realize an interrupt call without affecting the call quality on the call side and the interrupt side at all, and that it can contribute to the future development of time division switching equipment.

By using the time-division call path interruption method according to the present invention, multi-party calls (for example, conference call method), which were previously difficult to realize due to problems such as call loss and ringing due to impedance imbalance, can be realized. This function can also be realized relatively easily.

[Brief explanation of drawings]

FIG. 1 is a relay system diagram of one embodiment of the time-division channel interruption method according to the present invention, and FIG. 2 is a relay system diagram of another embodiment.
FIG. 3 is a relay system diagram of another embodiment, FIG. 4 is a principle diagram of voice mixing using voice mixing trunks in the time-division channel interruption system according to the present invention, and FIG. 5 is a diagram of voice mixing according to another embodiment. FIG. 6 is a block diagram of one embodiment of the audio mixing circuit in the trunk. FIG. 6 is a block diagram of another embodiment of the audio mixing circuit. 1.2...Subscriber telephone, 3a...Space-division type concentrator ladder switch, 3b...Time-division type concentrator ladder switch, 4...Distribution ladder switch,
5... Call trunk, 6... Interrupt trunk, 7... Analog/digital conversion point, 8
. . . Audio mixed trunk, 9 . . . Interrupt tone source, 10 . . . Subscriber trunk, 16 .
... Audio mixing circuit, 17 ... Serial-to-parallel conversion circuit, 18 ... Expander, 19 ... Adder,
20...Subtractor, 21...Compressor, 2
2...Parallel-serial conversion circuit,...1/3 reduction circuit. 3

Claims (1)

[Scope of Claims] 1. In a time-division exchange, one or more of the ladder switches constituting the communication route network includes a voice mixing means, and within the time-division exchange switch, a voice mixing means is provided. The communication path is opened, the lines in use are independently reconnected to the voice mixing means, the interrupt line is independently connected to the voice mixing means, and the voice mixing means is connected to each of the lines. 1. A time-division call path interruption method characterized in that each line is put into an interrupt call state by digitally mixing and distributing digital audio signals from the respective lines. 2. A time-division call path interruption system according to claim 1, in which the audio mixing means is housed in a time-division distribution ladder switch. 3. A time-division call line interruption system according to claim 1, in which the audio mixing means is housed in a time-division concentrator staircase switch. 4. In claim 1, 2, or 3, an interrupt tone identifying that an interrupt is in progress is sounded during an initial certain period of time in the interrupt call state or during the entire period during the interrupt call state. A time-division call path interruption method that connects to a mixing means and mixes and distributes the call audio signal to each line or a part of the line in the interrupted state. 5 Claims 1, 2, 3, or 4
In paragraph 1, the audio mixing means includes an audio mixing circuit, the audio mixing circuit receiving the digital audio signal and the digital interrupting tone signal from each line in the interrupting call state,
These are mixed digitally, and a mixture of digital voice signals from other lines except for each line's own and a digital interrupt tone signal as necessary is distributed and sent to each line in the interrupting call state. Time-division call path interruption method. 6 In claim 5, the audio mixing circuit is:
Digital audio signals to be mixed are received in a time-division manner, converted into parallel signal formats, added, subtracted from each digital audio signal itself, and then converted into serial signal format and time-divisionally converted. A time-division channel interrupt method that sends out signals on a regular basis. 7 In claim 6, the audio mixing circuit is
A time-division channel interrupt method that includes a level reduction circuit that optimizes the audio signal level of the addition or subtraction result. 8 In claim 6 or 7, the audio mixing circuit performs a companding operation after converting the input digital audio signal into a parallel signal format and before converting the input digital audio signal into a serial signal format. Time-division channel interruption method.