JPH0447817A - Digital private exchange system - Google Patents

Abstract

PURPOSE:To secure optimum transmission quality at a time corresponding to traffic and to effectively utilize an expensive digital repeating line by varying a band compression level. CONSTITUTION:Assuming that a call is newly generated between a subscriber terminal B1 and a subscriber terminal B2, although a repeating line 3 is already used. Central control parts 17 and 18 of PBX 1 and 2 checks it according to a built-in data table registered in advance whether there is any problem or not in communication due to terminals A1 and A2 already under communicating and in communication due to the terminals B1 and B2 to be set newly even when the band is compressed up to 32Kbps. When there is no problem, one channel of 64Kbps is handled as the two channels of 32Kpbs, and the communication is started between the terminals B1 and B2 without interrupting the communication between the terminals A1 and A2.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a digital private branch exchange system.

[Conventional technology]

Conventionally, when using digital relay lines in a digital private branch exchange system, in order to use the expensive digital relay lines as effectively as possible, signals that can be compressed, such as voice, are not kept at 64Kbps, but can be increased to 32Kbps. Generally, it is compressed and transmitted as much as possible.

[Problem to be solved by the invention]

However, in this type of usage of digital trunk lines, a predetermined band compression operation intervenes in any traffic state, for example, in a state where there are almost no calls.

Generally, when band compression is performed, deterioration in communication quality such as S/N deterioration and increase in transmission delay time is unavoidable.

Therefore, even though the traffic is sufficiently low and sufficient bandwidth is available for each call, the call quality is always degraded.

On the other hand, if excessive band compression is applied to a modem, facsimile, etc., normal operation may not be guaranteed even if there is no problem with voice communication. Therefore, in general, when transmitting modem and facsimile signals through a digital relay line, a line that does not perform the band compression mentioned above is reserved and is often used as a dedicated line for modems, etc. There is also the problem that the digital relay line cannot be used effectively depending on the facsimile traffic.

[Means to solve the problem]

The digital private branch exchange system of the present invention includes a standard PCM that is provided as an output of an 8-hour switch to each of a plurality of digital private branch exchanges each accommodating a subscriber terminal and connected via a digital trunk line and a common line signal line.
a first means for converting each of the signals into a desired band compression signal; and a second means for multiplexing the band compression signal from the first means into a bit string having the same transmission rate as the standard PCM signal. , third means for selecting at least one channel of the compressed band signal from the second means and the standard PCM signal and outputting the selected signal as an input to the time switch; fourth means for separating the compressed band signals that are multiplexed and input from the time switch; and fifth means for converting each of the compressed band signals from the fourth means into the standard PCM signal. , the time switch and the fifth
a multiplexing trunk having a sixth means for selecting at least one channel of the standard PCM signal from the means for inputting the signal to the time switch; a first control unit for transmitting and receiving call control information; a storage unit for registering band compression tolerance corresponding to the accommodated subscriber terminals; the time switch, the multiplex trunk and the first control unit; and a second control section that controls the control section.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

Referring to FIG. 1, which shows a digital private branch exchange system according to an embodiment of the present invention, 1 and 2 are independent digital private branch exchanges (PBXs), each of which transmits and receives call control information to and from a digital trunk line 3. They are connected by a common signal line 4. The subscriber terminals 5.6 are accommodated via subscriber circuits 7.8 in time division switches 9, 10, respectively. In addition, the digital trunk 11.12 and the multiplexed trunk 13.14 are connected to the time division switch 9.10.
is housed in. The above-mentioned constituent circuits of PBXl,2 are each controlled by a central control unit 17.18. The central control units 17.18 are respectively connected to common line signal control units 15.16.

Referring now to FIG. 2, the detailed configuration of the multiplex trunks 13, 14 shown in FIG. 1 is shown.

Bandwidth compression for inputting standard PCM signals from subscriber circuits via time switches in each of the multiplexed trunks 13, 14 to obtain band-compressed output signals (bandwidth compressed signals) of 32 K b ps and 16 Kbps. Part 2
0, a format unit 21 that multiplexes (multiplexes) the output of the band compression unit 20 into a bit string with the same transmission rate as the standard PCM signal, and selects the output of the format unit 21 and the standard PCM signal from the subscriber circuit. Line concentration function section 22
and are provided for sending signals to the digital trunk via the time division switch. If the signal sent to the digital trunk can be compressed, the band compression section 20. via the format section 21 and the line concentrator 22, or if it is a standard PCM signal, the line concentrator 2.
2 is selected and output.

On the other hand, if the signal input from the digital trunk via the time division switch is a standard PCM signal, the selector 23
is output to the port of the time switch which is selected by and sent to the subscriber circuit.

In addition, in the case of a compressed multiplexed signal, it is separated into 32 Kbps and 16 Kbps signals by the distributor 25,
The signal is input to a band expansion unit 24 for inverse conversion to a 64 Kbps standard PCM signal.

The output of the band expansion section 24 becomes the input of the selector 23. If the signal input from the digital trunk via the time division switch is a standard PCM signal, the signal is sent directly to the selector 23.
In the case of a compressed signal, the signal is decompressed and then output to the time switch port which sends it to the subscriber circuit.

Figure 3 shows the signal format on the digital trunk line 3 in Figure 1. Figure 3(a) shows the case where a 64Kbps standard PCM signal is transmitted as is, and 32Kbps
Figure 3 (
b), and 1 subscriber is 32Kbps, 2 subscribers is 16Kbps
FIG. 3(C) shows the case where the data is compressed to Kbps.

Next, referring to FIGS. 1, 2, and 3, PB
The digital relay line 3 between XI and PBX2 is 64K.
Assume that there is a transmission capability of bps.

Now, if only subscriber terminal (5) Al and subscriber terminal (6) A2 are in communication state, this trunk line 3 can be used at 64 Kbps for communication between terminals A1 and A2 without any problem ( Figure 3 (see a>).

The usage status of this trunk line 3 is PBXI and I) B
2 communicates via the common signal line 4,
Aligned.

Here, subscriber terminal (5) Bl and subscriber terminal (6) are newly added.
) Suppose that a call occurs with B2. However, relay port l
1I3 has already been used. Therefore, PBXI and PB
The central control units 17 and 18 of X2 control the communication by the terminals Al and A2 which are already in communication, and the newly set terminal B1.
Check whether there is any problem even if the bandwidth of B2 communication is compressed to 32Kbps using the pre-registered built-in data table. Treated as two channels of 32Kbps, terminal AI.

To start communication between terminals B1 and B2 without interrupting communication between A2.

Furthermore, assume that a communication request occurs between the terminals CI and C2. Relay port 113 is already full. Therefore, the central control unit 1
7.18 similarly starts checking whether it is possible to interrupt any of the communications between terminals A], A2, B1, and B2. It is assumed that communication between terminals C1 and C02 can be compressed to 16 Kbps without any problem. In addition, there is no problem with communication between terminals Bl and 82, but terminals Al and A2 handle communication by modem, and if data is registered that cannot be compressed below 32Kbps at present, the third Figure (c)
The multiplex trunk shown in FIG. 2 can be controlled using the signal format shown in FIG. 2 so that communication can be performed between the terminals Al and A2, the terminals B1 and B2, and the terminals C1 and C2.

Matching between the PBXIs 2 is also performed via the common signal line 4.

In the embodiment described above, the multiplicity change on the relay line is executed by interrupting the preceding communication without waiting for the completion of the communication, but there is no need to be limited to this. Further, the transmission speed on the trunk line may be other than 64.32°16 Kbps.

〔Effect of the invention〕

As explained above, according to the present invention, by making the band compression level variable, it is possible to ensure the optimum transmission quality at that point in time depending on the traffic, and to make effective use of expensive digital relay lines. can.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing the detailed configuration of the multiplexed trunk shown in the figure, and FIG. 3 is a diagram showing the signal format on the digital trunk line in the same embodiment. 1.2...Digital private branch exchange (PBX), 3...
・Digital relay line, 4...Common line signal line, 5.6
...Subscriber terminal, 7, 8...Subscriber circuit, 9,10
...Time switch, 11.12...Digital trunk, 13.14...Multiplex trunk, 15.16...
・Common line signal control unit, 17.18... Central control unit, 2
0... Bandwidth compression section, 21... Format section, 22
. . . line concentrator, 23 . . . selector, 24 . . . band expansion unit, 25 . . . distributor.

Claims (1)

[Claims] To each of a plurality of digital private branch exchanges each accommodating a subscriber terminal and connected via a digital trunk line and a common line signal line; the first converting each into the desired band compression signal;
means for multiplexing the compressed band signal from the first means into a bit string having the same transmission rate as the standard PCM signal; and means for multiplexing the compressed band signal from the second means and the standard PCM signal. third means for selecting at least one channel of a PCM signal and outputting it as input to the time switch; and the band compression signal multiplexed at the same transmission rate as the standard PCM signal and input from the time switch. fifth means for converting each of the band compressed signals from the fourth means into the standard PCM signals; a multiplexing trunk having a sixth means for selecting at least one channel of signals and inputting the selected signal to the time switch; a sixth means for transmitting and receiving call control information via the opposing digital private branch exchange and the common signal line; a first control unit; a first control unit having a storage means for registering band compression tolerance corresponding to the accommodated subscriber terminal; and controlling the time switch, the multiplexing trunk, and the first control unit; 2. A digital private branch exchange system comprising: 2 control units;