JPS61112448A - Data communication equipment - Google Patents

Abstract

PURPOSE:To improve the efficiency of a 2-wire line by providing a modulator- demodulator for both transmission and reception or transmission or reception only to the line of a data terminal equipment so as to select a proper one in response to the traffic. CONSTITUTION:Full duplex communication is attained between a data terminal device 1 and a center device 2 via the 2-wire line 3. The 1st modulator- demodulators 41, 51 having faster transmission speed than reception speed, the 2nd modulator-demodulators 42, 52 having faster reception speed than the transmission speed and the 3rd modulator-demodulators 43, 53 having equal transmission and reception speeds are provided to the line of the data terminal device 1 and the center device 2 and the center device 2 selects one of the modulator-demodulators of the data terminal device and center device sides in response to the traffic requested to each transmission direction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a data communication device that performs full-duplex communication between a data terminal device and a center device via a two-wire line.

Conventional configuration and its problems Traditionally, full-duplex communication was performed between data terminal equipment and central equipment such as a switching center via a relatively low-frequency line such as an existing two-wire subscriber telephone line (metallic cable). In this case, uplink and downlink links were secured through time division and frequency division. Regarding the allocation of communication speeds between uplink and downlink lines, there are two methods: a method that balances the two in consideration of the traffic type, and a method that unbalances the two. Furthermore,
The latter unbalanced system provides a system with a high uplink communication speed and, conversely, a system with a high downlink communication speed. However, in these unbalanced methods, the line with the lower communication speed is an extremely slow line used for returning communication control data, so these unbalanced methods are essentially used only for sending or receiving. It can be said that it is similar to the unidirectional communication method of

Therefore, users subscribe to one of three methods, depending on the type and mode of data communication they wish to perform: combination transmission and reception, transmission or reception.

[While I was wondering, 1.What is the conventional data communication device?
If the same user attempts to use the three communication methods mentioned above in combination depending on the traffic situation, it is necessary to install three subscriber lines in advance.4 As a result, the installation cost for line 01 is high. There is a problem in that not only does the usage rate of each line decrease. In order to reduce the cost of establishing a line, it may be possible to subscribe only to a compromise combination of transmitting and receiving methods, but if only transmitting or receiving is performed under this method, the amount reserved for receiving or transmitting is Since the other line is hardly used, the usage efficiency of the line as a whole decreases, and there is a problem that the line hold time becomes correspondingly longer.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the drawbacks of the prior art described above, and to provide a data communication device that improves the efficiency of a two-wire line.

Structure of the Invention In order to achieve the above object, the present invention provides three types of modulation/demodulation equipment for the line on the data terminal equipment side, one for both transmission and reception, one for transmission or reception bias, and selects the most suitable one or all depending on the traffic situation. 1 (that is, the present invention) is configured to flexibly use three types of modem equipment installed on the data terminal equipment side depending on the traffic situation, so only one subscriber line is required. Moreover, the line holding time can be minimized.

Example 1-8 Hereinafter, the present invention will be explained in more detail by way of examples.

FIG. 1 is a block diagram showing the configuration of an embodiment of a data communication device of the present invention. In the figure, 1 is a data terminal device, 2 is a center device, 3 is a two-wire full duplex line, 4 is a line termination device on the data terminal device 1 side, and 5 is a line termination device on the center device 2 side. .

The line termination device 4 on the side of the data terminal device 1 includes a first modem 41 whose transmission speed is higher than the reception speed, a second modem @ 42 whose reception speed is higher than the transmission speed, and a transmission speed and reception speed that are approximately the same. An equal third modulation/demodulation device 43 is provided. The three modem devices 41 to 43 are connected to the switching circuit 4
It is selectively connected to data terminal equipment 1 and line 3 via lines 4 and 45, respectively.

The line termination device 6 on the center equipment #2 side is also connected to the data terminal device 1.
Similarly to the line terminal device 4 on the side, a first modem 51 whose transmission speed is higher than the reception speed, a second modem 52 whose reception speed is higher than the transmission speed, and a second modem 52 whose transmission speed is almost equal to the reception speed. It is equipped with three modem devices 53.

Three modem devices 51 to 53, switching circuits 54 and 55
The terminals are selectively connected to the center device 2 and the line 3 via the respective terminals.

The operation of the meat system configured as described above will be explained separately for the operation when a call is sent from the data terminal device and the operation when a call is received to the data terminal device.

(1) Sending from a data terminal device When the user of the data terminal device 1 wants to send data to another data terminal device, information processing center, etc. (not shown) via the center device 2, the switching circuits 44 and 45 are activated. A transmission request is issued to the center device 2 using any of the modulation/demodulation devices 41 to 43 currently connected to the data terminal device 1 and the line 3 via the data terminal device 1 and the line 3. Center device 2,
When this transmission request is received using any of the modems 51 to 53 connected to the center device 2 and the line 3 via the switching circuits 54 and 56, the transmission request is sent to the switching lines 54 and 53 via the control line 21. drive and receive speed of large second
The second modem 52 is connected between the center device 2 and the line 3, and the second modem 52 is activated via the control line 22. However, if the second modem device 52 has already been selected and activated at the time of receiving the transmission request from the data terminal device 1 (d), the line termination device 5 is made to maintain the state 1. After this, , the center device 2 is the modem device 5
2 to return a reception preparation completion response to the data terminal device 1.

When the data terminal device 1 receives a reception ready response from the center device 2, it drives the switching circuits 44 and 45 via the control line 11, and selects the first modem device 41 with a high transmission speed.
is connected between data terminal equipment 1 and line 3, and K'
The first modem 41 is activated via the control line 12.

However, if the first modulation/demodulation device 41 has already been selected and activated at the time when the data terminal device 1 issues a call request, the line termination device 4 is caused to maintain that state.

Thereafter, the data terminal device 1 starts transmitting data using the first modem device 41 having a high transmission speed.

When the center device 2 detects that data other than communication control information has been sent back to the data terminal device 1 from another data terminal device or information processing center that is communicating with the data terminal device @1, the center device 2 Performs switching control of modem equipment such as.

That is, the center device 1 disconnects the first second modem 52, which has a high reception speed, from the center device 2 and the line 3, and
Instead, a third modem 53 having substantially the same transmission speed and reception speed is connected between the center device 2 and the line 3, and a third modem 63 is activated via the control line 22. Next, the center device 2 issues a modem/demodulator switching command to the data terminal device 1 . The data terminal device 1 which received this command, the first modem device 4 with a high transmission speed.
1, a third modem device 43 whose transmission speed and reception speed are approximately equal is connected to the data terminal device 1 and the line 3, and this modem device 43 is activated.

In this way, both the data terminal device 1 side and the data terminal device 1 side continue full-duplex communication by using all of the third modem devices 43 and 53 whose transmission speed and reception speed are approximately equal. After the end of this data communication, the line terminating device 4 on the data terminal device 1 side maintains the state in which the third modem device 43, which has almost the same transmission speed and reception speed, is connected to the data terminal device 1 and the line 3. drooping

On the other hand, if data other than communication control information is not transmitted to the data terminal device 1 from another data terminal device, etc. that is communicating with the data terminal device 1, the center device 2 switches the modem. do not have. Therefore, in this case,
The data terminal device 1 has a modem device 41 with a high transmission speed.
Continue only sending data using .

(2) Incoming call to a data terminal device From another data terminal device, etc. (not shown), the data terminal bag #
When a call arrives at the data terminal device 1, the center device 2 connects the modem device 51 with a high transmission speed to the line 3 and transmits the data to the data terminal device 1.
Notify of incoming calls. The data terminal device 1 that receives this incoming notification connects the modem device 42 with a high reception speed to the channel a3, and returns a response to the center device @2 indicating that the receiving cram school is completed.

In this way, after data transmission to the data terminal device 1 has started, the center device 2 sends information other than communication control information from the data terminal bag @1 to other data terminal devices, etc. currently communicating. When detecting that data has been returned, the following switching control of the modem is performed.

That is, the center device 2 disconnects the first modem 51, which has a high transmission speed, from the center device @2 and the line 3, and instead connects the third modem 53, which has almost the same reception speed, to the center device 2 and the line. Connect between 3 and start this. Next, the center device 2 issues a modem/demodulator switching command to the data terminal device 1 . Upon receiving this command, the data terminal device 1 replaces the second modem 42 with a high reception speed with a third modem device 42 with a transmission speed that is almost equal to the reception speed.
The modem 43 is connected to the data terminal device 1 and the line 3, and the modem 43 is activated.

In this way, the data terminal device 1 side also receives data from the center device 2.
The side also continues full-duplex communication using the third modem devices 43 and 53 whose transmission speed and reception speed are approximately equal. After the end of this data communication, the line terminating device 4 on the data terminal device 1 side connects the third
The modem 43 maintains a state in which it is connected to the data terminal device 1 and the line 3.

On the other hand, if data other than communication control information is not transmitted from the data terminal device 1 to another data terminal device with which it is communicating, the center device 2 does not switch the modem. Therefore, in this case, the data terminal device 1 continues only to receive data using the modem 42 having a high reception speed.

Furthermore, when a call is made from the data terminal device 1 or when a call is received to the data terminal device 1, after the modem is switched once, one of the traffic other than the uplink or downlink traffic control information is If disappears, accordingly,
Immediately after the above-mentioned outgoing or incoming call, the selected modem is selected again and activated.

In the configuration shown in the figure, the modem device 51 on the side of the center device 2
53 may be installed for each data terminal device, or each of a plurality of modulation/demodulation devices may be shared among a plurality of data terminal devices.

Effects of the Invention As explained in detail above, the data communication device of the present invention is equipped with three types of modem devices on the line on the data terminal device side, and selectively switches one of them depending on the traffic situation. Since the system is configured to use the 1$02 line, it has the advantage that the 1$02 line can be used efficiently and the system can be made more economical.

[Brief explanation of drawings]

The figure is a block diagram showing the configuration of a data communication device in an embodiment of the present invention. 1...Data terminal bag {revised, 2...Center device, 3...2-wire line, 4...Line termination device on data terminal device side, 5... ...Line termination device on the center device side, 41.51...First modem with high transmission speed, 42.52...-Second modem with high reception speed, 43.53... . . . A third modulation/demodulation device whose transmission speed and reception speed are approximately equal.

Claims (1)

[Claims] Full-duplex communication is performed between the data terminal device and the center device via the two-wire line, and a second channel whose transmission speed is higher than the reception speed is installed on each side of the data terminal device and the center device of the two-wire line. The center device includes a first modem and a second modem whose reception speed is higher than the transmission speed, and a third modem whose transmission and reception speeds are approximately equal, and the center device controls the data terminal according to the traffic situation. A data communication device characterized in that one of the modulation and demodulation devices on the device side and the center device side is selectively operated.