JPS63207239A - Data communication system - Google Patents

Abstract

PURPOSE:To decrease the number of lines at a center side by sending a signal to show the communication speed of MODEM from a slave station to the center before communication is started and selecting the MODEM corresponding to the communication speed at the center. CONSTITUTION:When a slave station 1 executes the calling, the number of a line 5 of a center 4 is dialed by a network control unit NCU11 of the slave station 1. At the center 4, an NCU 41 closes a line. When the line is closed, a MODEM 12 of the slave station l transmits an MF signal that a communication speed is 1200 bps, to the center 4. The center 4 gives an instruction to a change-over switch 49 and connects a 1200 bps MODEM 42 to the line. In the same way, when calling is executed from a slave station 2 and a slave station 3, in respective cases, a MODEM 44 of 2400 bps and a MODEM 4800 bps are selected by the change-over switch 49 and the communication is executed between the slave stations 2 and 3 and the center 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Light] (Industrial Field of Application) The present Light relates to an f-to-night communication system that performs data communication using a subscriber telephone network.

(Prior Art) There is a conventional data communication system as shown in FIG. 2 which performs data communication using a subscriber telephone network. As shown in the drawing, this data communication system includes slave stations 101,
102 and 103 are connected to the center 104 via an exchange 108. Exchange 108 and center 104 are times 1!10
Connected by 5,106°107. Child JiJ10
1 is network control unit (NCU) 111.1200bp
s modem 112. It consists of a terminal equipment (DTE) 113.

The slave stations 102 and 103 also have a similar configuration. However, child station 10
2.103 has a communication speed of 2400bpS and 480bpS, respectively.
A 0bps modem 122.132 is provided. Center 104 is NCU141゜143.145 and 1200b
ps modem 142.2400 bps modem 144,
4800 bps modem 146. and central processing bag fif
It consists of f (CPU) group 147.

In such a data communication system, one of the slave stations 1Ol
200bps terminal device 113 and 010 of center 104
When attempting to communicate with one of the groups 147, the slave station 10
1 to dial the number of the line 105 to which the 1200 bps modem 142 of the center 104 is connected to establish a line connection and then perform data communication. 240 of slave station 102
0bpS terminal device 123 and 010 group 1 of center 104
47, the slave station 102 dials the number 1i106 to which the 2400 bps modem 144 of the center 104 is connected, and data communication is performed. When the terminal device W1133 of slave station 103 is 4800bl)S, it is time 11! I dialed the i17 number, connected, and started communicating.

(Problem to be Solved by the Invention) However, in such a conventional data communication system, each 31Y+@4 wire 105.1 according to the speed is connected to the center side.
06.107 must be prepared in advance, which poses a problem in that the number of lines on the center side increases.

fhn, CCITT Complaint V22b i 5 (F) Some modems, such as the modem and V22 modem, communicate with each other before data communication to set the communication speed, but this The modulation method and communication speed when falling back to the modem's normal communication speed were limited to modems with the same communication speed.

The present invention has been made in view of these problems, and its purpose is to provide a data communication system with a small number of lines on the center side.

[Structure 1 of the Invention (Means for Solving the Problems) To achieve the above object, the present invention provides means for transmitting a communication speed signal of the modem of the slave station in the slave station, and a means for transmitting the communication speed signal of the modem of the slave station, and The present invention is characterized in that it includes means for detecting a speed signal, modems having various communication speeds, and means for selecting a modem corresponding to the detected communication speed from the detected communication speed.

(Operation) Before starting communication, a signal indicating the communication speed of the modem owned by the slave station is sent to the center from the slave station, and when this signal is detected at the center, a modem corresponding to this communication speed is selected. . Thereafter, communication is performed between the slave station and this center using the selected modem. Therefore, only one line needs to be prepared on the center side.

(Example) An embodiment of the present invention will be described in detail below based on the drawings.

FIG. 1 is a configuration block diagram of a data communication system according to an embodiment of the present invention, and as shown in the figure, slave stations 1.
2.3 and the center 4 are connected via an exchange 8. Further, the center 4 and the exchange 8 are connected by a single line 5. Slave station 1 is NCUll, 1200 bps modem 1
It has a 2° terminal equipment ff (DTE>13.multifrequency (MF) signal transmitter 14.

NCUll performs network control. Modem 12 is 1200bp
The signal is modulated and demodulated at a speed of s. The MF signal transmitter 14 sends information indicating the communication speed of the modem 12 of the child member 1 to the center 4 via the switching center 8 using an MF low signal. Slaves 82 and 3 also have the same configuration as slave station 1, but since the modem 22 of slave station 2 has a communication speed of 2400 bps, M
The F signal transmitter 24 sends a signal indicating a communication speed of 2400 bpS to the center. Similarly, since the modem 32 of the slave station 3 has a communication speed of 4800 bpS, the MF signal transmitter 34 sends a signal indicating this communication speed to the center 4.

Center 4 is NCU41.1200bl)S modem 42
, 2400bl) S modem 44, 4800 bps modem 46. CPU group 47. MF signal receiver 48. It has a changeover switch 49.

The MF receiver 48 receives the MF sent via the IPJ5.
Receive low signal. The changeover switch 49 is the MF receiver 48
In response to the signal indicating the communication speed received by the modem, the modem corresponding to the communication speed is selected. For example, the MF signal receiver 48
When it receives an MF low signal indicating a communication speed of 120.0 bps, the selector switch 49 is switched to the position shown by the solid line in the figure, and the 1200 bps modem 42 is connected.

Next, the operation of this embodiment will be explained. For example, when the slave station 1 makes a call, it dials the number Pi15 of the center 4 using the NCIJII of the slave station 1.

In the center 4, the NCU 41 detects the call and closes the line. Modem 1 of slave station 1 indicates that the line has been closed.
When 2 is detected, the MF @ signal signal 14 command is issued and the MF
The signal transmitter 14 transmits an MF signal to the center 4 indicating that the communication speed is 1200 bps. M at center 4
The F@ signal is received by the MF signal receiver 48, and the communication speed is 120.
It detects that it is 0 bps, issues an instruction to the selector switch 49, and connects the 1200bl) S modem 42 to the line. The modem 42 returns a response signal to the slave station 1, and the slave station 1 starts data communication after detecting this response signal.

Similarly, when a call is made from slave station 2 and slave station 3, the changeover switch 49 changes the -T-
The 7' modem 44 and the 4800 bps modem 46 are selected, and communication is performed between the child 82, 3 and the center 4.

As described above, in this embodiment, before starting communication, a signal indicating the communication speed of the modem possessed by the slave station is sent to the center side, and when the center side receives this signal, the modem with the communication speed corresponding to this signal is selected. Therefore, there is no need to provide a line for each modem communication speed as in the past, and processing can be performed using one line. Therefore, the initial construction cost and the monthly line usage fee can be reduced, and the NCU
It is general in that it can also reduce function.

In this embodiment, a data communication system to which three slave stations are connected has been described, but the number of slave stations is not limited to this. Furthermore, the type of communication speed of the modem is not limited to that of this embodiment. Further, the signal notifying the communication speed is not limited to this embodiment.

[Effect of the invention]

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a data communication system according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional data communication system. 1.2.3...Slave station, 4...Center. -E-7' of 12-1200 b p s. 14.24.34...MF signal transmitter. 22 ・2400 bos modem.

Claims (1)

[Scope of Claims] A data communication system in which a plurality of slave stations equipped with modems having various communication speeds and a center are connected via a switching center, and data communication is performed between the slave stations and the center. , the slave station is provided with means for transmitting a communication speed signal of a modem possessed by the slave station, and the center is provided with means for detecting the communication speed signal, modems having various communication speeds, and a means for transmitting a communication speed signal of a modem possessed by the slave station, and means for selecting a modem corresponding to the communication speed from the data communication system.