JP2002165242A - Digital exchange and its line interface board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely recognize the existence of a terminal device, when the terminal device is connected to a communication line, even if discrepancy of transmission rates occurs between the communication line and an interface part. SOLUTION: Transmission data of an up frame from an inner line terminal 2 is stored in a buffer 131, in an inner line interface circuit 13 by shuttle transmission. When a request for transmitting monitor data arrives from a central control unit 14, in order to confirm whether or not the transmission data is stored in the buffer 131, in other words, whether the inner line terminal 2 exists, state monitor data required therefor are notified from an inner line interface circuit 13 to the central control part 14. After that, when the central control unit 14 grasps that the transmission data have been stored in the buffer 131 from the notified state monitor data, existence of the inner line terminal 2 is recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital switching device for selectively switching and connecting a terminal device having a plurality of transmission rates, and a line interface board thereof.

[0002]

2. Description of the Related Art In recent years, key telephones and PBXs (Privat
In a digital telephone switching system using e-branch exchange, etc., a system that can handle signals of various transmission rates has been proposed in order to diversify services. In this case, a switching device is used which concentrates a plurality of communication ports in which a plurality of transmission rates are mixed at one place and selectively switches and connects them. This type of switching device is provided with a dedicated interface unit corresponding to various transmission rates so that the input side and the output side form a pair, and performs an exchange connection between the dedicated interface units determined for each transmission rate. ing.

However, in the above-described conventional switching device, the maximum number of lines for each transmission rate is predetermined, and therefore, the expandability is poor. For example, the addition of communication ports due to an increase in extension telephones, a new transmission rate However, there is a problem that it is not possible to flexibly cope with the addition of the communication port.

[0004] That is, since the maximum number of lines for each transmission rate is predetermined, even if there is an idle line in the exchange,
It is not possible to connect a communication port with a transmission rate that is higher than that. In order to solve this, the design of the configuration of the dedicated interface unit on the input side and the output side is inevitably changed, and the cost is greatly increased.

[0005] In the event that a transmission rate mismatch occurs between the dedicated interface unit and the communication port, even if the communication port is later replaced with a corresponding communication port, the exchange recognizes that the terminal does not exist and disconnects the communication. And transmission may be impossible forever.

[0006]

As described above, in the conventional switching device, since the maximum number of lines for each transmission rate is predetermined, the expandability is poor, and the addition of a communication port due to an increase in the number of extension telephones. However, there is a problem that it is not possible to flexibly cope with the addition of an extension telephone having a new transmission rate.

In the event that a transmission rate mismatch occurs between the dedicated interface unit and the communication port, even if the communication port is later replaced with a corresponding communication port, the exchange recognizes that the terminal does not exist and performs communication. Will be cut off, and transmission will be impossible forever.

Therefore, a first object of the present invention is to provide a communication system in which a terminal device is connected to a communication line even if a transmission rate mismatch occurs between the communication line and the interface unit.
It is an object of the present invention to provide a digital exchange device and its line interface unit capable of reliably recognizing the presence of a terminal device.

A second object of the present invention is to provide a digital exchange apparatus and a line thereof capable of flexibly coping with the addition or modification of an existing transmission rate terminal apparatus and the addition of a new transmission rate terminal apparatus. An object is to provide an interface board.

[0010]

The digital exchange according to the first aspect of the present invention can connect a digital communication line to which a terminal device can be connected at an end, and can communicate with the terminal device connected to the digital communication line. A plurality of line interface units for transmitting and receiving transmission data, and an exchange control unit connected to the plurality of line interface units via an internal bus and for comprehensively controlling processing relating to exchange connection between the plurality of line interface units. In order to achieve the first object, each of the plurality of line interface units is provided with transmission data storage means for storing a predetermined amount of transmission data arriving from the terminal device, Between the unit and a plurality of line interface units, the control required to detect whether or not the transmission data is stored in the transmission data storage means. A control information transmitting / receiving means for transmitting / receiving information via an internal bus, and a terminal for detecting, from a result of transmission / reception of control information by the control information transmitting / receiving means, that the terminal device is connected to the line interface via a digital communication line And means for confirming existence.

According to the first aspect of the present invention, as long as the terminal device is connected to the digital communication line, even if the transmission rates do not match between the line interface unit and the terminal device, the transmission data from the terminal device can be obtained. Is reliably stored in the buffer in the line interface unit. And
Between the exchange control unit and the plurality of line interface units, whether the transmission data is stored, that is, the control information necessary to confirm whether the terminal device is present,
The switching control unit is notified from the plurality of line interface units.When the switching control unit recognizes that the transmission data is stored in the line interface unit from the notified control information, the switching control unit transmits the digital communication line. It becomes possible to recognize the presence of the terminal device to be connected.

Therefore, the exchange control unit does not directly transmit and receive transmission data for confirming existence with the terminal device, but stores the received transmission data in the line interface unit to which the terminal device is connected. It is a configuration that recognizes the existence of the terminal device only by checking whether or not there is
Even if the transmission rates do not match between the communication line and the interface unit, the presence of the terminal device can be reliably recognized when the terminal device is connected to the communication line. Also, since the exchange control unit does not check the contents of the transmission data transmitted and received between the line interface unit and the terminal device, it is configured to grasp the existence of the transmission data,
There is no need to provide the exchange control unit with a high-performance processor capable of supporting various transmission rates, and a general-purpose processor can perform sufficient processing.

[0013] In a second aspect of the present invention, the control information transmission / reception means inquires from the exchange control section whether or not the transmission data is stored in the transmission data storage means to a plurality of line interface sections. On the other hand, a function to return response information indicating the presence or absence of transmission data from the line interface unit to the switching control unit is provided, and the terminal existence confirmation unit performs digital communication only when the response information indicating the presence of transmission data is received. This is to detect connection to a line interface unit via a line.

According to the second aspect, when the exchange control unit inquires whether transmission data is stored, the exchange control unit transmits response information indicating the presence or absence of transmission data from the terminal device. , It is not necessary to use an interface designed with high reliability for the circuit interface unit, and the circuit interface can be realized with an inexpensive interface.

Further, in order to achieve the second object,
In the digital switching device according to the third aspect of the present invention, in the above object, each of the plurality of line interface units includes reception data storage means for receiving and storing transmission data from the terminal device, and transmission data to be transmitted to the terminal device. Transmission data storage means for capturing and storing the transmission data, and writing the transmission data to be stored in the reception data storage means to the reception data storage means so as to have a transmission rate arbitrarily designated by the exchange control unit, and Transmission rate conversion control means for causing the transmission data stored in the means to be output from the transmission data storage means so as to have a transmission rate arbitrarily specified by the exchange control unit, wherein the exchange control unit comprises a plurality of line interface units. Monitoring means for monitoring the presence or absence of transmission data stored in each received data storage means; When the transmission data is stored in the reception data storage unit, the transmission control unit reads the transmission data from the reception data storage unit, and the transmission rate conversion control unit of the corresponding line interface unit responds to the transmission rate setting request. And a transmission rate designating means for designating a transmission rate.

According to the third aspect, the exchange control unit includes:
A transmission rate is individually specified for a plurality of line interface units, and each line interface unit transmits transmission data coming from a terminal device at a transmission rate specified by an exchange control unit.
That is, the data is written into the reception data storage means at a transmission rate that can be handled by the exchange control unit, and the transmission data stored in the transmission data storage means is transmitted at the transmission rate specified by the exchange control unit.
In other words, it is possible to read out at a transmission rate corresponding to the terminal device and output it to the terminal device connected to the digital communication line. That is, transmission data of different transmission rates can be shared by the same switching control unit.

For this reason, when the terminal device connected to the digital communication line is changed to a terminal device having a new transmission rate, it is not necessary to replace the terminal device with a line interface unit corresponding to the new transmission rate. Since a new transmission rate can be specified for the line interface unit to which the terminal device is connected, there is no need to make any changes to the switching unit.

Further, since the transmission rates of a plurality of line interface units can be variably set by one switching control unit,
As long as there are free lines, it is possible to easily cope with the increase in the number of terminal devices. Furthermore, even if a terminal device requesting a new transmission rate appears in the future, it is only necessary to specify the corresponding transmission rate from the switching control unit to the corresponding line interface unit.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a main configuration of a digital switching system provided with a line interface board according to the present invention.

As shown in FIG. 1, the digital exchange system is constructed by arbitrarily connecting a plurality (up to i) extension terminals 2 (2-1 to 2-i) to a digital exchange device 1. I have.

The digital exchange 1 further includes a time switch 11, a plurality of (j) central office interface circuits 1
2 (12-1 to 12-j), a plurality (i) of extension interface circuits 13 (13-1 to 13-i), a central control unit 14, and a time switch 11, a station line interface circuit 12, The extension interface circuit 13
They are connected to each other via the CM highway 15.

The time switch 11, the office line interface circuit 12, the extension interface circuit 13, and the central control unit 14 are connected to one another via a data highway 16.

The time switch 11 arbitrarily switches and connects the office line interface circuit 12 and the extension line interface circuit 13 by exchanging time slots on the PCM highway 15 under the control of the central control unit 14.

The office line interface circuit 12 is connected to office lines L (L-1 to Lj) such as public lines and dedicated lines as required. The office line interface circuit 12 performs an office line interface operation on the connected office line L. The office line interface operation includes conversion of an audio signal (analog) provided via the office line L into a PCM signal, conversion of a PCM signal provided via the time switch 11 into an audio signal (analog), office line L , And transmission of various signals to a network connected via the office line L. The office line interface circuit 12 exchanges various control information related to the office line interface operation with the central control unit 14 via the data highway 16.

The extension interface circuit 13 includes, for example, a digital extension (2B) used as a digital communication line.
The extension terminal 2 is connected as necessary via the (channel + D channel). The extension interface circuit 13 performs an extension interface operation for the connected extension terminal 2. The extension interface operation includes extracting a PCM signal output from the extension terminal 2 from the PCM highway 15,
This includes monitoring the state of the extension terminal 2 and sending various signals to the extension terminal 2. Also, the extension interface circuit 1
3 exchanges various control information relating to the operation of the extension interface with the central control unit 14 via the data highway 16.

The central control unit 14 controls each unit of the digital exchange device 1 in a centralized manner so that the digital exchange device 1
The operation as is realized.

(First Embodiment) This embodiment is similar to FIG.
Extension interface circuit 13 and central control unit 1
4

FIG. 2 is a block diagram showing a specific connection configuration between the extension interface circuit 13 and the central control unit 14 in the first embodiment.

That is, the extension interface circuit 13 of the first embodiment includes a buffer 131 and control information transmitting / receiving means 132.

On the other hand, the central control unit 14 includes a control information transmission / reception unit 141 and a terminal presence confirmation unit 142.

The buffer 131 stores 1 from the extension terminal 2.
The transmission data of the frame is stored. The control information transmission / reception means 132 transmits control information necessary for detecting whether or not transmission data from the extension terminal 2 is stored in the buffer 131 to / from the central control unit 14.
Send and receive via.

On the other hand, the control information transmitting / receiving means 141 of the central control unit 14 is required to detect whether or not the transmission data from the extension terminal 2 is stored in the buffer 131 with the extension interface circuit 13. Control information is transmitted and received via the data highway 16.

The terminal presence confirming means 142 receives the control information transmitted and received by the control information transmitting and receiving
The extension terminal 2 is connected to the extension interface circuit 13 via the extension.
It detects that it is connected to.

Next, the operation of the above configuration will be described with reference to FIG.
This will be described with reference to FIG.

That is, the extension interface circuit 13
As shown in (1), the transmission data of one frame is always transmitted by the ping-pong transmission method regardless of the presence or absence of the extension terminal 2. Here, if the extension terminal 2 exists (2)
As shown in (2), the transmission data of the upstream frame is returned, but if not present, the transmission data is not returned. Therefore, the extension interface circuit 13 stores the transmission data of the upstream frame in the buffer 131. Thus, the presence / absence of the extension terminal 2 is determined. The transmission data of the upstream frame stored in the buffer 131 is
Updated for each round trip of ping-pong transmission.

On the other hand, when confirming the presence of the extension terminal 2, the central control unit 14 makes an inquiry to the extension interface circuit 13 as shown in (3). That is, the central control unit 14 transmits a request for sending monitoring data to the extension interface circuit 13 to confirm whether or not the extension terminal 2 exists.

Each time a request for sending monitoring data from the central control unit 14 arrives, the extension interface circuit 13 uses the latest monitoring information at that time, that is, information indicating the occupancy of the buffer 131 as status monitoring data (4 ) Is sent from the extension interface circuit 13 to the central control unit 14.

Then, the central control unit 14 determines whether or not the extension terminal 2 is connected to the extension interface circuit 13 based on the received state monitoring data.

Therefore, even if a transmission rate mismatch occurs between the extension interface circuit 13 and the extension terminal 2, the central control unit 14 keeps the extension terminal 2 connected to the extension interface circuit 13 as long as the extension terminal 2 is connected to the extension interface circuit 13. Can be confirmed.

As described above, according to the first embodiment, as long as the extension terminal 2 is connected to the extension interface circuit 13, the transmission rate inconsistency between the extension interface circuit 13 and the extension terminal 2 is not affected. Even if it occurs, the transmission data of the upstream frame from the extension terminal 2 is surely stored in the buffer 131 in the extension interface circuit 13 by the ping-pong transmission. A buffer 131 is provided between the central control unit 14 and the extension interface circuit 13.
Is transmitted from the extension interface circuit 13 to the central control unit 14 in order to confirm whether or not the transmission data is stored in the extension interface 2, that is, whether or not the extension terminal 2 is present. When the central control unit 14 recognizes that the transmission data is stored in the buffer 131 from the notified state monitoring data, the central control unit 14 can recognize the presence of the extension terminal 2.

For this reason, the central control unit 14 does not directly transmit / receive transmission data for confirming the presence of the extension terminal 2 to / from the extension terminal 2, but stores the extension in the buffer 131 of the extension interface circuit 13 to which the extension terminal 2 is connected. Since the configuration is such that the presence of the extension terminal 2 is recognized only by confirming whether or not the transmission data received from the terminal 2 is stored,
Even if a transmission rate mismatch occurs between the extension terminal 2 and the extension interface circuit 13, the central control unit 14 can reliably recognize the presence of the extension terminal 2 as long as the extension terminal 2 is connected.

Further, since the central control unit 14 does not check the contents of the transmission data transmitted and received between the extension interface circuit 13 and the extension terminal 2 but grasps the existence of the transmission data stored in the buffer 131, There is no need to replace the central control unit 14 with a high-performance processor, and a general-purpose processor can sufficiently perform processing.

Further, the extension interface circuit 13
When a request to send monitoring data from the central control unit 14 arrives, it is only necessary to notify the central control unit 14 of status monitoring data indicating the occupancy of the buffer 131. Therefore, the extension interface circuit 13 is designed with high reliability. There is no need to use an interface, and an inexpensive interface can be used.

(Second Embodiment) The second embodiment relates to the extension interface circuit 13 and the central control unit 14 in FIG.

FIG. 4 is a block diagram showing a specific connection configuration between the extension interface circuit 13 and the central control unit 14 in the second embodiment.

The extension interface circuit 13 shown in FIG.
(13-1 to 13-i) include a separation circuit 21, a serial / parallel conversion circuit (S / P conversion circuit) 22, a reception buffer 23, a reception control circuit 24, and a transmission rate generation circuit 2.
5, a multiplexing circuit 26, a parallel / serial conversion circuit (P / S conversion circuit) 27, a transmission buffer 28, and a transmission control circuit 29.

Here, a communication port to which the extension terminal 2 is connected is connected to the separation circuit 21. Then, the separation circuit 21 extracts the transmission data of the 2B + D channel arriving via the communication port and separates the data into three serial signals.

The S / P conversion circuit 22 converts serial data including D-channel data among serial signals supplied from the separation circuit 21 into parallel data based on a transmission rate reference clock supplied from the transmission rate creation circuit 25. The data is converted and given to the reception buffer 23.

The reception buffer 23 includes a central control unit 14.
Is connected to the data highway 16. The reception buffer 23 stores the parallel data supplied from the S / P conversion circuit 22 in a storage area corresponding to the write signal output from the reception control circuit 24. Further, the reception buffer 23 supplies the control data in the parallel data stored in the storage area corresponding to the read address output from the central control unit 14 to the central control unit 14.

On the other hand, the transmission buffer 28 is connected to the data highway 16 to which the central control unit 14 is connected. The transmission buffer 28 stores control data provided from the central control unit 14 in a storage area corresponding to a write address provided from the central control unit 14. The write address is also notified to the transmission control circuit 29.

The transmission buffer 28 supplies control data stored in a storage area corresponding to the read signal output from the transmission control circuit 29 to the P / S conversion circuit 27.

The P / S conversion circuit 27 converts the parallel data including the control data supplied from the transmission buffer 28 into serial data based on the transmission rate reference clock supplied from the transmission rate creation circuit 25,
Give to.

The multiplexing circuit 26 is connected to a communication port to which the extension terminal 2 is connected. Then, the multiplexing circuit 26
Multiplexes the serialized control data supplied from the P / S conversion circuit 27 with the PCM data of the 2B channel and sends it to the communication port.

The transmission rate creating circuit 25 is connected to the data highway 16 to which the central control unit 14 is connected. Then, the transmission rate creation circuit 25 sends the central control unit 1
4, a transmission rate reference clock for converting the transmission data from the extension terminal 2 into a transmission rate that can be handled by the central control unit 14 is generated based on the transmission rate arbitrarily designated from S.4. P conversion circuit 2
2 and the reception control circuit 24. Further, the transmission rate creation circuit 25 generates a transmission rate reference clock for converting the control data from the central control unit 14 into a transmission rate that can be handled by the extension terminal 2, and converts this transmission rate reference clock into a P / S conversion circuit 27. And the transmission control circuit 29.

On the other hand, the central control unit 14 has a monitoring function, a read control function, and a transmission rate designating function.

The monitoring function monitors the presence / absence of data stored in the reception buffer 23 of each of the i extension interface circuits 13.

The read control function is used when the data is stored in the reception buffer 23 by the monitoring function.
The data is read from the reception buffer 23.

The transmission rate designating function is performed by, for example, a transmission rate creation circuit 25 of the extension interface circuit 13 in response to a transmission rate setting request input from the maintenance terminal.
Specify the transmission rate for.

Next, the operation of the extension interface circuit configured as described above will be described.

That is, regarding the transmission operation, the central control unit 14 writes the transmission data into the transmission buffer 28,
The transmission control circuit 29 is activated to start transmission. The transmission control circuit 29, which has started transmission, outputs a read signal to the transmission buffer 28 in accordance with the transmission rate reference clock generated from the transmission rate creation circuit 25, and then outputs the read signal to the P / S conversion circuit 27. On the other hand, it outputs a load signal of parallel input data. Then, the transmission data output from the transmission buffer 28 is taken into the P / S conversion circuit 27. Thereafter, the P / S conversion circuit 27 converts the transmission data supplied from the transmission buffer 28 into serial data in accordance with the transmission rate reference clock supplied from the transmission rate creation circuit 25, and transmits the serial data to the multiplexing circuit 26. give.

On the other hand, in the receiving operation, data arriving from the extension terminal 2 is separated by the separation circuit 21, and the separated data is transmitted by the S / P conversion circuit 22 to the transmission rate reference given from the transmission rate creation circuit 25. The data is converted into parallel data according to the clock. At the same time, when detecting the presence of the received data, the S / P conversion circuit 22 activates the reception control circuit 24. The reception control circuit 24 outputs a parallel data latch signal to the S / P conversion circuit 22 when the processing of the S / P conversion circuit 22 ends.

Thereafter, the reception control circuit 24 outputs a write signal to the reception buffer 23, and causes the output data of the S / P conversion circuit 22 to be taken into the reception buffer 23.

The central control unit 14 monitors the presence / absence of data in the reception buffer 23 of each extension interface circuit 13 and reads out the received data from the reception buffer 23 if there is data.

Here, for example, it is assumed that the extension terminal 2 connected to the communication port 2 is changed to an extension terminal having a new transmission rate. Then, the maintenance person of the digital switching device 1 notifies the central control unit 14 of the identification number indicating the communication port 2 and the changed transmission rate of the terminal device through the maintenance terminal. Then, the central control unit 14 specifies a new transmission rate to the transmission rate creation circuit 25 of the extension interface circuit 13 corresponding to the communication port 2. Thereafter, by executing the above processing procedure, the transmission data of the new transmission rate can be handled by the central control unit 14.

As described above, according to the second embodiment, the central control unit 14 individually specifies the transmission rate for the i extension interface circuits 13 and each extension interface circuit 13 The transmission data coming from 2 is parallelized by the S / P conversion circuit 22 at the transmission rate designated by the central control unit 14, that is, the transmission rate that can be handled by the central control unit 14, and written into the reception buffer 23.
The transmission data stored in the transmission buffer 28 is transferred to the transmission rate designated by the central control unit 14, that is, the extension terminal 2
, And serialized by the P / S conversion circuit 27.
It can be multiplexed with the CM data and output to the extension terminal 2. That is, transmission data of different transmission rates can be shared by the same central control unit 14.

Therefore, when the extension terminal 2 connected to the communication port is changed to a terminal device having a new transmission rate, it is not necessary to replace the extension interface circuit with an extension interface circuit corresponding to the new transmission rate. Extension interface circuit 13 connecting the terminal device
, It is only necessary to specify a new transmission rate.

The transmission rate creation circuit 25 of the i extension interface circuits 13 is controlled by one central control unit 14.
Can be set variably, so long as there is an idle line, extension terminal 2
Can easily be accommodated. In the future,
Even if a terminal device requesting a new transmission rate appears, it is only necessary to specify the corresponding transmission rate from the central control unit 14 to the corresponding extension interface circuit 13.

(Other Embodiments) The present invention is not limited to the above embodiments. For example, in the first embodiment, the example has been described in which the extension interface circuit notifies the central control unit of state monitoring data indicating the occupancy of the buffer when the central control unit issues a monitoring data transmission request. Alternatively, state monitoring data indicating the occupancy of the buffer may be transmitted from the extension interface circuit to the central control unit at regular intervals.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0071]

As described above in detail, according to the present invention, as long as the terminal device is connected to the digital communication line, even if the transmission rate mismatch between the line interface unit and the terminal device occurs, the terminal device can perform the communication. Is reliably stored in the buffer in the line interface unit.
Control information necessary for confirming whether or not transmission data is stored between the exchange control unit and the plurality of line interface units, that is, whether or not a terminal device is present, includes a plurality of line information. The switching unit is notified from the interface unit. When the switching control unit recognizes that the transmission data is stored in the line interface unit from the notified control information, the switching control unit is connected to the digital communication line. It becomes possible to recognize the presence of the terminal device.

Therefore, according to the present invention, even if a transmission rate mismatch occurs between the communication line and the interface unit,
When the terminal device is connected to the communication line, the presence of the terminal device can be surely recognized.

Further, in another invention, the switching control unit individually specifies a transmission rate for a plurality of line interface units, and each line interface unit specifies transmission data coming from a terminal device by the switching control unit. At the transmission rate, that is, the transmission rate that can be handled by the exchange control unit, and writes the transmission data stored in the transmission data storage unit at the transmission rate specified by the exchange control unit, that is, the transmission rate corresponding to the terminal device. And outputs it to a terminal device connected to a digital communication line.

Therefore, according to the other invention, it is possible to flexibly cope with the addition or change of the terminal device of the existing transmission rate and the addition of the terminal device of the new transmission rate.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of a digital switching system including a line interface board according to the present invention.

FIG. 2 is a block diagram showing a specific connection configuration between an extension interface circuit and a central control unit according to the first embodiment.

FIG. 3 is a view for explaining operations of an extension interface circuit and a central control unit shown in FIG. 2;

FIG. 4 is a block diagram showing a specific connection configuration between an extension interface circuit and a central control unit according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Digital exchange apparatus, 11 ... Time switch, 12 (12-1 to 12-j) ... Office line interface circuit, 13 (13-1 to 13-i) ... Extension interface circuit, 14 ... Central control part, 15 ... PCM highway, 16 data highway, 21 separation circuit, 22 serial / parallel (S / P) conversion circuit, 23 reception buffer, 24 reception control circuit, 25 transmission rate creation circuit, 26 multiplex circuit, 27: parallel / serial (P / S) conversion circuit, 28: transmission buffer, 29: transmission control circuit, 131: buffer, 132, 141: control information transmission / reception means, 142: terminal presence confirmation means.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) H04Q 3/42 104 H04L 13/00 307C 5K101 F term (reference) 5K030 HA01 HB06 HC04 HC13 KA03 KA13 5K034 AA20 CC06 EE09 FF08 HH21 MM08 5K049 AA07 BB04 BB23 CC04 5K050 BB12 BB14 CC04 HH03 5K051 AA02 AA04 CC01 DD13 FF02 JJ02 JJ03 5K101 LL02 MM04 NN21 SS01 TT03

Claims (6)

[Claims] 1. A digital communication line to which a terminal device can be connected can be connected to an end, a plurality of line interface units for transmitting and receiving transmission data to and from the terminal device connected to the digital communication line, and An exchange control unit connected to the line interface unit via an internal bus, and comprehensively controlling a process related to exchange connection between the plurality of line interface units, wherein each of the plurality of line interface units includes A transmission data storage unit for storing a predetermined amount of the transmission data arriving from a terminal device, wherein the transmission data storage unit stores the transmission data between the exchange control unit and the plurality of line interface units; Control information transmitting / receiving means for transmitting / receiving control information necessary for detecting whether or not the control information is transmitted via the internal bus; And a terminal presence confirming means for detecting that the terminal device is connected to the line interface unit via the digital communication line, based on a result of transmission and reception of the control information by the digital switching device. . 2. The control information transmitting / receiving means inquires from the switching control section whether or not the transmission data is stored in the transmission data storage means to the plurality of line interface sections. A function of returning response information indicating the presence / absence of the transmission data from the line interface unit to the switching control unit; the terminal presence confirming means only transmits the response information indicating the presence of the transmission data; 2. The digital switching device according to claim 1, wherein the digital switching device detects that the device is connected to the line interface unit via the digital communication line. 3. A plurality of line interface units for transmitting and receiving transmission data to and from the terminal device connected to the terminal device, wherein a digital communication line connectable to a terminal device can be connected to an end. An exchange control unit connected to the line interface unit via an internal bus, and generally controlling a process related to exchange connection between the plurality of line interface units; and each of the plurality of line interface units includes: Receiving data storing means for capturing and storing transmission data from the terminal device; transmitting data storing means for capturing and storing transmission data to be transmitted to the terminal device; and transmitting data to be stored in the reception data storing means. Writing into the reception data storage means so that the transmission rate is arbitrarily designated by the exchange control unit. Transmission rate conversion control means for outputting the transmission data stored in the transmission data storage means from the transmission data storage means so as to have a transmission rate arbitrarily specified by the exchange control unit, Monitoring means for monitoring the presence or absence of transmission data stored in the reception data storage means of each of the plurality of line interface units; and when the transmission data is stored in the reception data storage means by the monitoring means, Reading control means for reading the transmission data from the reception data storage means; and transmission rate designating means for designating a transmission rate to a transmission rate conversion control means of a corresponding line interface unit in response to a transmission rate setting request. A digital exchange device. 4. A plurality of line interface units for transmitting and receiving transmission data to and from a terminal device connected to the terminal device, wherein a digital communication line connectable to a terminal device can be connected to the terminal. A line used as the line interface unit in a digital switching device that is connected to the line interface unit via an internal bus and includes an exchange control unit that comprehensively controls processing related to the exchange connection between the plurality of line interface units. In the interface board, between the transmission data storage means for storing a predetermined amount of the transmission data arriving from the terminal device, and the exchange control unit, whether or not the transmission data is stored in the transmission data storage means Control information transmission / reception control means for transmitting / receiving control information required for detection via the internal bus Line interface board, characterized by comprising. 5. The control information transmission / reception control means, when receiving an inquiry from the exchange control section as to whether or not the transmission data is stored in the transmission data storage means, transmits the transmission information to the exchange control section. 5. The line interface board according to claim 4, having a function of returning response information indicating the presence / absence of data. 6. A plurality of line interface units for transmitting and receiving transmission data to and from the terminal device connected to the digital communication line, which can connect a terminal device to the terminal. A line used as the line interface unit in a digital switching device that is connected to the line interface unit via an internal bus and includes an exchange control unit that comprehensively controls processing related to the exchange connection between the plurality of line interface units. In the interface board, a reception data storage unit that fetches and stores transmission data from the terminal device, a transmission data storage unit that fetches and stores transmission data to be transmitted to the terminal device, and that is stored in the reception data storage unit. The transmission data to be transmitted is set to the transmission rate arbitrarily specified by the exchange control unit. And writing the transmission data stored in the transmission data storage unit from the transmission data storage unit to a transmission rate arbitrarily designated by the exchange control unit. A line interface board comprising: rate conversion control means.