JPH04199954A - Key telephone system - Google Patents

Abstract

PURPOSE:To reduce the burden on a central processing part by selecting data terminals selected by means of the extension designation signal of dial service and MODEM having an attribute corresponding to the data terminals at the time of an incoming call from trunk lines to a system and forming data channels between the terminals and MODEM first. CONSTITUTION:At the time of incoming call by using dial-in service from the trunk lines 251-25m, the data terminals 371-37n designated by the extension designation signal of dial-in service and MODEM 431-43j whose attributes agree with the data terminals are selected before a call signal is given to MODEM 431-43j and the channels between them are connected. Since the data terminals 371-37n and MODEM 431-43j become the same state as that where they are directly connected as it were, a control command is transmitted/received, is analyzed and is controlled based on the analysis between both data terminals and MODEM. Thus, it becomes unnecessary for data interfaces 311-31j and 351-35n and the central processing part 49 of a system to participate in the processings. Thus, the load on the central processing part is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a key telephone system having a plurality of data terminals as extensions.

(Prior Art) This button telephone device is provided with a MODEM for modulating and demodulating data in order to enable communication between an extension data terminal and the public telephone network.

In this case, it is uneconomical to provide an expensive MODEM for each terminal, so it is recommended to pool one or a few MODEMs and communicate with the pooled MODEM only when communicating with the public telephone network. The system selectively connects the data terminals that are used. This is called modem pooling.

In such a conventional system, when a call is made from a data terminal or when a call is received from the network, a central control unit that controls call processing and switching communicates with the MODEM and the data terminal through R3-2, respectively.
Send and receive control commands via the 32D interface,
The transmitted and received data of these R5-232Ds are analyzed, and based on the results, call processing such as MODEM mode control, data terminal calling, and communication path connection between the two is controlled.

Furthermore, in parallel with this, it also controls the communication path connection between the MODEM and the network. At this time, MODEM performs automatic call/receive operations according to procedures such as CCITT recommendation V and 25bis. In this case, in order to prevent data loss, etc., it is necessary to finely control the order and timing of connection of communication channels.

(Problem to be Solved by the Invention) As described above, in a button telephone system that uses conventional modem pooling, the processing that the central control unit must perform when making and receiving calls is complex, resulting in a heavy load. be.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the load on the central processing unit when making and receiving calls in a key telephone system in which modems are pooled.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a system that is connected to a central office line that can provide a dial-in service, has a plurality of data terminals connected to the extension line, and allows these data terminals to access the central office line. Two or more MODEMs are pooled, and these MODEMs have a built-in network control device and a function to perform automatic call/receive procedures for the data terminals, and also have communication paths between the central office lines, data terminals, and MODEMs. A button telephone system comprising exchange means for forming and disconnecting, comprising: terminal attribute storage means for storing attributes of each of the data terminals; MODEM attribute storage means for storing attributes of each of the MODEMs; When a call arrives, terminal selection means selects one data terminal based on a dial-in service extension designation signal given from the central office line, and an attribute of the selected data terminal is determined by referring to the terminal attribute storage means. Recognized,
One MODEM with attributes matching this attribute
is selected by referring to the MODEM attribute recognition means.
DEM selection means; and controlling the exchange means to form a communication path between the selected data terminal and the selected MODEM, so that the communication path between the selected data terminal and the selected MODEM is controlled. a first exchange control means for making it appear as if the selected data terminal and the selected MODEM were directly connected; and a MODEM calling means for giving a calling signal to the selected MODEM after forming a communication path between the selected data terminal and the selected MODEM. and, upon receiving the response of the selected MODEM to the paging signal, controls the switching means to form a communication path between the selected MODEM and the central office line, thereby communicating with the selected data terminal. and second exchange control means for forming a communication path between the office lines via the selected MODEM.

(Function) In the system of the present invention, when a call is received using the dial-in service from a central office line, before giving a paging signal to the MODEM, the data terminal specified by the extension designation signal of the dial-in service is Attribute or matching MODEM
is selected and the communication path between the two is connected. As a result, the data terminal and MODEM are in the same state as if they were directly connected, so control commands are sent and received between the two, their analysis, and control based on them, and the data interface and system central There is no need for the processing section to be involved, and the load on them is reduced.

(Embodiment) FIG. 1 shows a system configuration of an embodiment of a key telephone system according to the present invention.

The main device 1 includes a control unit 3 that mainly controls call processing and communication path switching, and a data highway 5 that is a transmission path for control data.
, PCM highway 7 which is a time division communication path, and various interface units 9゜11.13, 15, 17.
Contains 19. Specifically, these interface units are connected to central office lines 25□ to 25II of the public telephone network (analog network).
Office line interface unit 111 for connecting
~11, Digital telephone interface unit 13□~ to which digital telephone 27□~27 and data interface unit 31 are connected as extensions.
13o, 17, and a standard telephone interface unit 21 for connecting a standard telephone as an extension.

Digital telephone interface unit 13 of main device 1
1 to 1B, a total of n digital telephones 27, to 27n are connected to one interface unit, for example, eight telephones. Each digital telephone 27 includes a telephone circuit 33 that has a function of internally converting audio signals in the form of digital signals to and from the main device 1, and a telephone circuit 33 and the main device 1. It also has a built-in data interface unit 35 that relays communication of digital signals between the two. Data interface unit 35
The data terminal 37 having an R5-232D ink face can be connected to this.
R5-232D transmission data (S
D) and received data (RD) into the format of data communicated with the main device 1.

This system includes j modems (MODEM) 43,
~43j are pooled.

MODEM4B, ~43j are devices that modulate and demodulate data in order to enable the data terminal 37 with the R5-232D interface to enter the public telephone network, and have a built-in network control unit (NCU) and are compatible with the R3-232D. It is possible to carry out call/receive procedures for data terminals using sent data (SD) and received data (RD). These MO'DEMs 43, -43j are divided into several groups according to their data rates. For example, 300
It is divided into three groups, each having a data rate of 1200bps, 1200bps, and 2400bps.

The terminal for connecting to the public telephone network of each MODEM4B is the main unit 1.
connected to the standard telephone interface unit 21 of
On the other hand, a data terminal connection terminal is connected to the digital telephone interface unit 17 of the main device 1 via the data interface unit 31. Furthermore, this MODE
The data interface unit 31 interposed between the M43 and the digital telephone interface unit 17 has a configuration similar to that of the data interface unit 35 in the digital telephone 27 except for differences in details, and has a similar configuration to the data interface unit 35 in the digital telephone 27. R5-232D communicated
It has a function of converting the transmitted data (SD) and received data (RD) of the digital telephone interface unit 17 into a data format to be exchanged with the digital telephone interface unit 17.

The control unit 3 in the main device 1 includes four microcomputers that control call processing, and a time switch that interconnects time-division communication paths in the PCM highway and exchanges voice and data under the control of the microcomputer 49. circuit 5
1, and the MP signal (selection signal mixed with two frequencies) sent from the office line 25, and the microcomputer 49
includes an MF receiver 53 that communicates with the MF receiver 53 .

In this system, when the data terminal 37 performs data communication with an external data device through the public telephone network, the central office line 25 - office line interface unit 11 - PCM highway 7 - standard telephone interface unit 21 - M
ODEM43←→R5-232D interface 47←
-Data interface unit 31-→Digital telephone interface unit 17^PCM highway 7-
A communication path is formed along the route of digital telephone interface unit 13←→data interface unit 35-→R5-232D interface 39←→data terminal 37.

One feature of this system is that when forming the communication path in response to an incoming call from the central office line 25, the dial-in service provided by the public telephone network is used to minimize the burden on the microcomputer 49. The point is that the communication path is formed according to the following procedure.

The configuration of each part of this system will be explained in detail below.

FIG. 2 shows the configuration of the data interface unit 35 within the digital telephone 27.

This data interface unit 35 includes a ping-pong transmission circuit 55 for half-duplex communication of digital signals with two wires with the digital telephone interface unit 13 of the main device 1, and a telephone control microcomputer that controls the telephone circuit 33. 57, a data communication control microcomputer 59 that controls the data terminal 37, and an R3-2 that performs level conversion of various signals communicated with the data terminal 37 through the R5-232D interface 39;
32D interface driver/receiver 61, etc.

The ping pong transmission circuit 55 has two B channels (Bl, B2 channel) with a speed of 64 Kbps and a 16 Kb
2B+D consisting of one D channel with a speed of p s
A digital signal is transmitted to and from the main device 1 in a ping-pong manner using a time-division channel of this type. This ping pong transmission circuit 4
As shown in FIG. 3, reference numeral 9 denotes a 2B+D creation circuit 65 that receives upstream data from each channel, synthesizes it into a data packet in the 2B+D format, and sends it to the main device 1, and
It has a 2B+D separation circuit 67 that receives a downlink data packet in the 8+D format and separates it into data for each channel. Here, the B1 channel is used for transmitting voice data transmitted and received by the telephone circuit 33 during a call on this telephone, the B2 channel is used for transmitting communication data transmitted and received by the data terminal 37 during data communication, and the D channel data is transmitted from the telephone Control and data communication control microcomputers 57 and 59 are assigned to transmit and receive control data. That is,
The audio data sent from the telephone circuit 33 during a call is B.
Communication data sent from the data terminal 37 during data communication is used as 1-channel upstream data Bl-IN, B2-channel upstream data B2-IN, and control data output from the microcomputer 57.59 is D-channel upstream data D. -IN, each enters the 2B+D creation circuit 63, where they are created into 280 packets and sent to the main device 1. Further, the 2B+D packet that entered the 2B+D separation circuit 65 from the main device 1 is separated here into 81 channel downlink data B1-0UT, 82 channel downlink data B2-0UT, and D channel upstream data D-IN. It is sent to telephone circuit 33, data terminal 37 and microcomputer 57.59.

B2 channel downlink and uplink data B2-0UT, B2
-IN is 8-bit serial data (64Kb)
ps), of which 6 bits are communication data (48
Furthermore, the downlink data B2-0UT contains the received carrier detection signal CD (8Kbps) of R5-232D and the transmission enable signal C8 (8Kbps) as the remaining 2 bits.
), and the upstream data B2-IN includes a transmission request signal R3 (8 Kbps) and a transmission enable signal C5 (8 Kbps) of R3-2B2D as the remaining 2 bits. and,
The downlink data B2-0UT is first input to the serial/parallel converter circuit 69 and separated into communication data, received carrier detection signal CD, and transmittable signal C8, and the communication data is further manually inputted to the parallel/serial converter circuit 71.
The data is returned to Kbps serial data. The data communication data is first input to the serial/parallel conversion circuit 73 and converted into 64 Kbps parallel data, and then input to the parallel/serial conversion circuit 75 where it is combined with the transmission request signal R5 and the transmission enable signal C8. 8-bit upstream data B2-IN is created.

The telephone control microcomputer 57 has a function of controlling the telephone circuit 33 (for example, ringing a bell, turning on/off various displays, etc.) based on the downlink data D-OUT of the D channel, and controlling signals from the telephone circuit 33. (for example, hook signal, selection signal, etc.)
It has a function to output to. Under the control of the telephone control microcomputer 57, the selector 63 selects control data from either the telephone control microcomputer 57 or the data communication control microcomputer 59, and outputs it as D channel uplink data D-IN. It is sent to the ping pong transmission circuit 55. Telephone control microcomputer 5
When transmitting control data, 7 controls the selector 63 to select its own transmission control data, and also prohibits the data communication control microcomputer 59 from transmitting control data. Therefore, while the telephone control microcomputer 57 is not transmitting control data, the data terminal control microcomputer 59 is allowed to transmit control data, and the control data is transmitted to the main device 1 through the D channel.

The data communication control microcomputer 59 controls the data terminal 37 based on the D channel downlink data D-OUT.
A function to control the called indication signal CI and data set ready signal DR of the R3-232D interface to be given to the R3-232D interface, a function to create and output control data to be sent to the data terminal 37, and a command reception mode. It has a function to select communication mode. Here, the command reception mode is a mode in which only the data communication control microcomputer 59 accesses the transmission data SD and reception data RD of the R3-232D. On the other hand, the communication mode is a mode in which the transmission data SD and reception data RD of the R3-232D are transmitted and received to the main device 1 in a transparent manner through 82 channels. This mode selection is specifically performed by selectors 65 and 67 placed under the control of the data communication control microcomputer 59. That is, in the communication mode, the selector 65
selects the downlink communication data from the parallel/serial conversion circuit 71 as the received data RD, and the selector 67 selects the transmission data SD of R5-232D and converts it into serial/serial data.
It is sent to the parallel conversion circuit 73. On the other hand, in the command reception mode, the selector 65 selects the control data from the five data communication control microcomputers as the received data RD, and the selector 67 selects a high level constant signal (meaning no data) from the power supply ■. Select.

The data terminal control microcomputer 59 further includes:
It also has the function of creating control data to be sent to the main device 1 based on the terminal ready signal ER of R3-232D from the data terminal 37 and the transmission data SD, and sending it to the ping-pong transmission circuit 55 as D channel uplink data D-IN.

FIG. 4 shows a detailed configuration of the data communication control microcomputer 59.

This microcomputer 59 has a ping-pong transmission circuit 5.
D channel downlink data D-OUT from 5 is received by the D channel receiving section 77, and the destination address included in this received data is sent to the address analyzing section 79. The address analysis section 79 opens the gate 81 when the destination address is the address of the data communication control microcomputer 59, and closes the gate 81 when the destination address is the address of the telephone control microcomputer 57. When the gate 81 opens, the D channel downlink data D-IN is sent to the data analysis section 83. According to the data analysis result in the data analysis section 83, C
The I control unit 85 controls the called display signal CI of the R8-232D, the DR control unit 87 controls the data set day signal DR, and the data control unit 89 outputs control data or receives commands. mode or communication mode is switched. The mode selection signal is set to a low level in the communication mode, and set to a high level when a command is received, and is applied to the gate 95 through the input terminal 91. Therefore, the gate 95 is opened only in the command reception mode, and the control data from the data control section 89 is sent to the data terminal 37 as the received data RD of R5-232D.

The data monitoring section 97 receives the transmission data SD from the data terminal 37 through the gate 93, analyzes it, and sends the result to the data creation section 99.

This data monitoring section 97 receives a mode selection signal,
As will be described later, the type of data to be monitored differs depending on the command reception mode and communication mode. In the communication mode, when the data monitoring section 97 receives special data, it notifies the data analysis section 127 of this fact, and the data analysis section 127 thereby switches the mode selection signal from the communication mode to the command mode.

The ER monitoring unit 101 receives the terminal ready signal E of R5-232D.
R is monitored and data indicating whether the data terminal 37 is ready or not is sent to the data creation section 99. The data creation section 99 creates D channel data to be sent to the main device 1 according to the received data, and this D channel data is given to the gate 103. The gate 103 is kept open under the control of the telephone control microcomputer 57 only while the telephone control microcomputer 57 is not transmitting control data. When the gate 103 is open, the D channel data created by the data creation section 99 is sent to the D channel transmission section 105, and then sent to the ping pong transmission circuit 55 through the selector 63 as D channel upstream data D-IN.

The automatic call making/receiving procedure is based on sending data SD and receiving data RD.
``Call,''``Receive,''``Answer,''``Connect,'' and ``Call.''
This is a procedure in which control data called commands such as a dial signal, a disconnection request, and a call termination are sent and received between the data terminal 37 and the data interface unit 35, thereby proceeding with call connection and recovery processing. When the data interface unit 35 is on standby, it is in the command reception mode, so the data communication control microcomputer 59
or monitor and control the above commands. During call connection processing, the data interface unit 35 transitions from the mote to the communication mote for receiving commands. After once transitioning to the communication mode, the data communication control microcomputer 59 monitors only the "disconnection request" and "end of call" commands, and upon receiving this command, the command reception mode returns. CCITT Recommendation V, 2 for automatic call/receive procedures.
There are 5bis procedures etc.

Figure 5 shows R3-232D interface 4 of modem 43.
7 to the digital telephone interface unit 17 of the main device 1.
The configuration of 1 is shown.

This data interface unit 31 is the data interface unit 35 for the data terminal explained in FIG.
The main difference is that the latter is set in modem mode for data terminal 37, whereas the former is set in terminal mode for modem 43.

In other words, the direction of the signal line of the R5-232D interface is reversed. Furthermore, since this data interface unit 31 is not built into the telephone, the 81 channels for voice data transmission are not used, and it does not have a telephone control microcomputer, but has two channels for telephone control and data communication control. There is no selector for selecting uplink control data).

FIG. 6 shows the configuration of the digital telephone interface unit 13 in the main device 1 for connecting the digital telephone 27. As shown in FIG. Note that the digital telephone interface unit 1 for connecting the data ink interface unit 31
7 also has a similar configuration.

This interface unit 13 includes, for example, eight ping pong transmission circuits 149 to 1498, each of which is connected to the data interface unit 35 of each of the eight telephones 27 via a data transformer 151 for digital transmission. Ping-pong transmission is performed using a time-division channel in the 2B+D format between the two. This ping-pong transmission circuit 149 has the same configuration as the ping-pong transmission circuit 55 in the data interface UniSoto 35 shown in FIG. 3, or the latter operates in slave mode.
The former operates as a master mote. In other words, the ping-pong transmission circuit 149 in master mode takes the initiative in transmitting packets for ping-pong transmission.

The time slot assigner 153 receives a frame synchronization signal and a clock from the PCM highway 7 and notifies each ping pong transmission circuit 149 of the timing for transmitting and receiving the upstream and downstream data of the B channel to the PCM highway 7. Each ping-pong transmission circuit 149 directly accesses the PCM channel 7 at a time specified by the time slot assigner 153 to transmit and receive upstream and downstream data at a speed of 2.048 Mbps.

The control data communication microcomputer 155 is in charge of monitoring p-channel data (control data) transmitted and received by each ping-pong transmission circuit 149 and communicating the control data with the control unit 3 via the data highway 5.

FIG. 7 shows the configuration of the standard telephone interface unit 21 to which the MODEM 43 is connected.

The calling signal sending circuit 251 has a calling signal generation source 253.
The calling signal (16Hz AC signal) supplied from M
This is a circuit for sending data to the ODEM 43. The DC power supply circuit 255 supplies a specified DC voltage to the MODEM 43,
This circuit inverts the polarity and detects whether the DC loop is open or closed. The dial detection section 257 is a circuit that detects dial pulses.

The codec 259 performs A/D and D/A conversion of audio signals, and transmits and receives audio data to and from the PCM highway 7 at the time specified by the time slot assigner 261.

The control data communication microcomputer 263 controls sending/stopping of a calling signal, monitors opening and closing of a DC loop, controls polarity reversal, monitors dial pulse detection results, and exchanges control data with the control unit 3 via the data highway 5. It is used for communication.

One standard telephone m interface unit 21 is equipped with, for example, eight sets of a calling signal sending section 25, a DC power supply circuit 255, a dial detecting section 257, and a codec 259, and can be connected to a maximum of eight MODEMs 43.

FIG. 8 shows the configuration of the office line interface unit 11 for connecting the office line 25. As shown in FIG.

The interface circuit 237 is a call signal detection circuit 239
, is equipped with a polarity reversal detection circuit 241 and a DC loop circuit 243, and is connected to the central office line 25 of the public telephone network, and is capable of detecting a calling signal from the central office line 25, detecting polarity reversal of the central office line 25, and closing/closing the DC loop. Open and send a dial pulse to the central office line. The codec 245 is an audio signal A/D and D/A
This converts the central line 2 using the DC loop circuit 243.
By closing the DC loop 5, it is coupled to the central line 25 in an alternating current manner. For example, four sets of these interface circuits 237 and codecs 245 are installed in one office line interface unit 11.

The time slot assigner 247 determines the timing for transmitting and receiving audio data to and from each codec 245 or the PCM highway 7 based on a predetermined time slot address for each codec, a frame synchronization signal from the PCM highway 7, and a clock, and Notify codec 245.

Each codec 245 has a time slot assigner 247
Audio data is transmitted and received with the PCM highway 7 at the time specified by.

The control data communication microcomputer 249 monitors the detection signals of the call signal detection circuit 239 and the polarity inversion circuit 241, controls the DC loop circuit 243, and performs call signal detection and polarity inversion with the control unit 3 via the control data highway 5. Sends and receives control data related to detection, DC loop opening/closing, dial pulse transmission, etc.

FIG. 9 shows the configuration of a portion of the microcomputer 49 that is involved in call processing when an incoming call is received using the dial-in service from the central office line 25. When receiving dial-in service, the central office line interface unit 11 of the main device
The sequence of communication performed between the station line 25 and the central office line 25 is defined by the network. The sequence of this communication is shown in FIG.

Before explaining FIG. 9, the sequence shown in FIG. 10 will be briefly explained. When a call is received, the polarity of the office line is inverted and then a paging signal is input from the office line 25 to the office line interface unit 11 in this order. After that, when the office line interface unit 11 sends the primary response signal to the office line 25, the office line 25
An extension designation signal (a 1- to 4-digit MF multiplied signal indicating the extension number is sent from
Then, when a secondary response signal (DC loop closure) is sent, a telephone call (data communication) is started.

Next, the microcomputer 49 will be explained with reference to FIG.

The receiving section 281 receives control data from various interface units in the main device through the data highway 5 and analyzes it.

The four microcomputers have a terminal speed and busy table 285 and a M O D M speed and busy table 313. Terminal speed and busy table 285
is the extension number (200) of each data terminal 371-37.
, 201 etc.) and data speed (1200 bps, 24
00bps, etc.) and the status of busy or free (busy: 1,
Empty: 0) is written. The MODEM speed and busy table 313 contains the extension numbers (300, 301, etc.) and data speeds (1200b, etc.) of each MODEM 43 to 43j.
ps, 300bps, etc.) and status (busy: 1, empty: O
) is described.

When the data terminal 37 changes from a busy state to an idle state, a "connectable" command is sent from the digital telephone interface unit 13 to the receiving section 281. When this command is received, the table rewriting unit 283 writes "0" indicating an empty state in the corresponding extension number column of the terminal speed and busy table 285.

Regarding the MODEM 43, when the mode changes from the busy state to the standby state, a "connectable" command is manually input to the receiving section 281 from the data interface unit 31 connected to the MODEM 43. Then, the table rewriting unit 28
3 writes "0" to the MODEM speed and busy table 313, indicating an empty state.

When the polarity is reversed and a paging signal arrives from a specific office line predetermined for data communication, for example, 25, to the office line interface unit 111, an "incoming call" command is sent from the office line interface unit 11 to the receiving unit 281. Sent. Then, the time switch control section 3
17 controls the time switch circuit 5 to form a communication path between the office line interface unit 111 and the MF signal receiver 53 in the control unit 3. At the same time, the command sending unit 319 instructs the office line interface unit 111 to send a primary response signal to the office line 25□.

After that, when an extension designation signal arrives from the office line 25 in the form of an MF multiplied signal, this extension designation signal is received by the MF channel μ53 and analyzed. is given to the extension number receiving section 321 and stored in the register 323. This stored extension number is analyzed by the extension number analysis unit 325, and
ODEM selection 291 is notified.

The terminal/MODEM selection unit 291 refers to the terminal continuity and busy table 285 and determines the status of the data terminal (hereinafter referred to as the selected data terminal) having the extension number notified by the extension number analysis unit, for example, 37□. Check.

If the selected data terminal 37□ is empty, the terminal/MODEM selection unit 291 next refers to the MODEM busy table 313 and selects the selected terminal 37□.
One free MODEM (referred to as selected MODEM), for example 43, is selected from the MODEM group having the same data rate as . And the terminal/MO
The DEM selection unit 291 notifies the command sending unit 327 and the time switch control unit 329 of the extension numbers of the selected terminal 37□ and the selected MODE M43□.

As a result, the command sending section 327 sends the "rMODEM connection" command to the selected MODEM 4B and the data interface units 311 and 351 connected to the selected data terminal 37□, respectively, and the time switch control section 329 connects the time switch circuit. 51 to connect the selected MODE M2S and the selected data terminal 37□. Further, the table rewriting unit 283 updates the selected terminal 37 and the selected MODEM 43 in the terminal busy table 285 and the MODEM busy table 313.
Write "1" in the status column of □ to indicate a busy state.

After these operations are completed, the command sending unit 333 sends the selected MODEM 43. A "calling signal" command is sent to the standard telephone interface unit 21 connected to the standard telephone interface unit 21, and a command "extension designation reception complete" is sent to the office line interface unit 11.

Thereafter, when the selected data terminal 371 answers the call, an "answer" command is manually input from the standard telephone interface unit 21 to the receiving section 281. Then, the command sending unit 335 or the central office line interface unit 11
．． to close the DC loop (send the secondary response signal),
MODEM 4B selected by the time switch control unit 337 or the time switch circuit 51 and the central office line 25
, connect between. The data terminal 37 selected in this way,
A communication path for data communication between the caller and the calling data device is formed.

When terminating data communication from the data terminal 37,
A command "Loop Open" is input from the standard telephone interface unit 21 to the receiving section 281. Then, the command sending unit 339 sends this "loop open" command to the central office line interface unit 111, and also sends a "disconnection instruction" command to the data interface unit 31.
Send to 1°351. At the same time, the time switch control section 34
1 controls the time switch circuit 51 and MODEM4
3 and the office line 25 □ and between MODEM 43 and the data terminal 37 are disconnected.

Next, referring to FIG. 11, the specific station line 2 for data communication
The operation of the system when a call is received using the dialing service from 51 will be explained.

The data interface unit 35 in each digital telephone 27 constantly monitors the ready state of the data terminal 37 during standby, and when the terminal ready signal ER turns on, the data communication control microcomputer 59 detects this. At the same time as turning on the data set ready signal DR to the data terminal 37, the control unit 3 in the main device
Sends a "Connectable" command to. In the main device 1, when the microcomputer 49 in the control unit 3 receives this "connectable" command, it writes "0" in the column of the terminal speed and busy table 285 for the corresponding terminal. Similarly, MODEM43 and data interface unit 3
The ready status of both is monitored even for one hour. During standby, the data interface unit 31 always turns on the terminal ready signal ER. And M.O.D.E.
When M43 turns on the data set ready signal DR, the microcomputer 109 in the data interface unit 31 detects this and sends a "connectable" command to the control unit 3 in the main device. When the microcomputer 49 in the main unit receives this command, it sets "0" in the MODEM speed and busy table.
”.

When a polarity reversal and a calling signal arrive at the main device 1 from the specific station 25 for data communication, the microcomputer 249 in the office line interface unit 11 recognizes this as a dial-in incoming signal and sends the "incoming call" command to the control data controller. It is sent to the control unit 3 in the main device through the iway 5.

When the microcomputer 49 in the control unit 3 receives the "incoming call" command, it activates the time switch circuit 51.
is controlled to exchange data between the time slot assigned to the office line interface unit 111 and the time slot assigned to the MF receiver 53, that is, to connect the office line 25 and the MF receiver 53. Furthermore, the computer 2 in the central office line interface unit 111
49, the central office line 25. A primary response signal is sent to the Then, from the station line 25, 1 of the MF times signal format
A four-digit extension designation signal arrives and is input to the MF receiver 53.

The MF receiver 53 analyzes the received MF multiplied signal and notifies the microcomputer 49 of the designated extension number as a result. When the microcomputer 49 receives the extension number, it uses the table 285 to check the status of the data terminal, for example 371, selected by the extension number. If the selected terminal 371 is free, the selected terminal 371
Read the data rate of. Next, the microcomputer 49 refers to the modem speed and busy table 313 and selects a free one from the MODE M group having the same data speed as the selected data terminal 37.
Select the MODE M, for example 43. After this, the selected data terminal 371 and the selected MODE
M43 sends the "rMODEM connection" command to the connected data interface units 31 and 351. Also, a busy bit "1" is written in the status columns of the selected terminal 37□ and MODEM 431 in both tables 285 and 313. Furthermore, the time switch circuit 51
The time slot assigned to the data terminal 37 selected for , and the time slot assigned to the selected MODEM 431 are exchanged, that is, the connection between the selected data terminal 37 and the selected MODEM 43 □ is commanded. do.

In the data interface unit 351, when the microcomputer 59 receives the "rMODEM connection" command, the selector 65. 67 to set the communication mode. Similarly, the communication mode is set in the data interface unit 311 as well.

Thus, MODEM 431-R3-232D interface 471-data interface unit 31
．． -Digital telephone interface unit) 17-P
CM Highway 7 - Digital telephone interface unit 131 - Data interface unit 351
- Three RS-232D interfaces - A data communication path between the MOD EM 43 and the data terminal 37 is formed by the route of the data terminal 37□.

When the above processing is completed, the microcomputer 49 in the main device connects to the standard telephone interface unit 21.
by controlling the computer 263 in the MODEM 43.
．． send a call signal to. Furthermore, the central office line interface unit 111 is controlled to send an extension designated reception completion signal (DC loop disconnection) to the central office line 25.

If MODEM43□ receives the above call signal, it will turn R.
3-232D sends an "incoming call" command as received data RD (from MODEM 43. to data interface unit 311). This command is received by the data terminal 37 via the aforementioned data communication path. If the data terminal 37 receives this command, the R5-232
It sends an "incoming call response" command as the transmission data SD of D, and waits for the arrival of a "connection" command.

When the MODEM 43 receives the "response to incoming call" command from the data terminal 371, it closes the DC loop and responds, and also transmits a "connect" command as the received data RD.

When the computer 49 in the main device recognizes the closure of the DC loop by MODE M2S, it controls the station line interface unit 11 to send a secondary response signal (to close the DC loop) to the station line 25□. send it out. moreover,
Exchange between the time slots assigned to the central office line interface unit 111 and the time slots assigned to the standard telephone interface unit 21 for the time switch circuit 51, i.e. central office line 251 and MODEM
43. instructs the formation of a communication path between

Communication between the calling data device and the data terminal 37 is thus started via the office line 25□.

〔Effect of the invention〕

As explained above, according to the present invention, when a call is received from the central office line to the system, the data terminal selected by the extension designation signal of the dial-in service and the M
By selecting ODEM and first forming a data communication path between the terminal and MODEM, the two are connected as if they were directly connected, so control and analysis of control commands associated with outgoing and receiving calls is done by that terminal. Data terminal and MODEM
As a result, the burden on the data interface unit and the central processing unit in the system is reduced.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing the overall configuration of an embodiment of the key telephone system according to the present invention, and FIG. )
3 is a block diagram showing the configuration of the ping-pong transmission circuit in FIG. 2, FIG. 4 is a block diagram of the data communication control microcomputer 59 in FIG. 2, and FIG. is a block diagram showing the configuration of the data interface unit (DIU) for MODEM in FIG. 1, FIG. 6 is a block diagram showing the configuration of the digital telephone interface unit in FIG. 1, and FIG. is the first
FIG. 8 is a block diagram showing the configuration of the standard telephone interface unit (STU) in the figure; FIG. 8 is a block diagram showing the configuration of the central office line interface unit (COU) in FIG. 1;
Figure 9 is a block diagram showing the main part configuration of the microcomputer of the control unit in Figure 1, Figure 10 is a communication sequence chart between the office line and the system when receiving dial-in service, and Figure 11 is FIG. 2 is a sequence diagram illustrating the operation of the system of FIG. 1; 1... Main unit (KSU), 3 control unit, 1
1... Office line interface unit (COU), 13
．． 17・Digital telephone interface unit, 21
...Standard telephone interface unit (STU)
, 27...Digital telephone, 31...(MODEM)
data interface unit (for data terminal), 35...-interface unit (for data terminal), 37...data terminal (DTE), 43...-MODEM, 49...
Microcomputer, 51... Time switch circuit, 53... MF signal receiver, 281... Receiving section, 2
83... Table rewriting unit, 285... Terminal speed and busy table, 291... Terminal/MODEM selection unit, 313... MODEM speed and busy table,
317, 329° 337.341... Time switch control section, 319° 327.333, 335, 339...
Command sending unit, 321... Extension number receiving unit, 323...
...Register, 325...Extension number analysis section. Applicant's agent Mr. Sato

Claims (1)

[Scope of Claims] 1. Two or more MODEMs connected to a central office line capable of providing dial-in service, with a plurality of data terminals connected to the extension, and for enabling these data terminals to access the central office line. These MODEMs have a built-in network control device and have the function of performing automatic call/receive procedures for the data terminals, and also form and disconnect communication paths between these office lines, data terminals, and MODEMs. A button telephone system comprising switching means, comprising: terminal attribute storage means for storing attributes of each of the data terminals; MODEM attribute storage means for storing attributes of each of the MODEMs; terminal selection means for selecting one data terminal based on an extension designation signal for dial-in service given from the line; and recognizing the attribute of the selected data terminal with reference to the terminal attribute storage means;
A MODEM that selects one MODEM having an attribute that matches this attribute by referring to the MODEM attribute recognition means.
selecting means; controlling the switching means to form a communication path between the selected data terminal and the selected MODEM, thereby controlling the switching means to form a communication path between the selected data terminal and the selected MODEM;
After forming a communication path between the DEMs as if they were directly connected, and the selected data terminal and the selected MODEM, the selected M
MODEM calling means for giving a calling signal to an ODEM; upon receiving a response from the selected MODEM to the calling signal, controlling the switching means to form a communication path between the selected MODEM and the central office line; A button telephone system characterized by comprising second switching control means for thereby forming a communication path between the selected data terminal and the office line via the selected MODEM. 2. The system according to claim 1, wherein the terminal attribute storage means further stores a busy or empty status of each data terminal, and the MODEM attribute storage means stores a busy or empty status of each MODEM. The MODEM selection means further stores the state of the selected data terminal stored in the terminal attribute storage means, and the state stored in the MODEM attribute storage means is empty. Only when there is at least one free MODEM, select one MODEM from among the free MODEMs that has attributes matching the selected data terminal.
A button telephone system featuring the selection of .