JPS61100062A - Telephone-data composite exchange system - Google Patents

Abstract

PURPOSE:To attain telephone/data communication with excellent characteristics by combining a frequency multiplexing circuit using a filter with a packet loopback circuit in a telephone exchange network. CONSTITUTION:A signal from telephone sets 101-10n passes through corresponding low-pass filters 611-61n and is connected to a PBX80 via transmission lines 411-41n and low pass filters 621-62n. A signal transmitted from data communication equipments 311-31n passes through high pass filters 711-71n, 721-72n and a loopback device 90 and is transferred to a destination data terminal device. Since the transferred signal passes through the high pass filters, a code with less DC component is used.

Description

[Detailed description of the invention] (Industrial application field) This invention relates to a combined telephone and data exchange system.

(Prior Art) Private exchanges (hereinafter referred to as PBX) have traditionally been used as a means of communication within premises.

On the other hand, local area networks (hereinafter referred to as LANs) have come to be used as devices that mainly perform data communication within premises. As a data communication system in LAN, for example, Japanese Patent Application Laid-Open No. 58-648 filed by Mizu Applicant
There is one disclosed in Publication No. 47. This data communication method uses a two-wire cable and performs data exchange by packet multiplexing technology using a folding device, and this technology will be described in detail later as it is also used in this invention.

Conventionally, a combined exchange system that uses a telephone network and LAN to perform combined exchange of telephone calls and data has not been proposed for the following reasons.

(Problems to be solved by the invention) PBX was originally designed for telephone exchange, and cannot be used as a means of data exchange due to its narrow bandwidth, which makes high-speed communication impossible, and data transmission errors due to pulse noise. There were disadvantages such as easy occurrence.

On the other hand, if a LAN is introduced, data communication with good characteristics can be achieved, but it requires the installation of a new communication network separate from the telephone network within the premises, resulting in high costs.

Therefore, the present invention was made to solve the problems of the prior art as described above, and its purpose is to utilize the transmission line for telephone communication already installed in the premises.
To provide a means for performing data communication with good characteristics independently of telephone communication while performing telephone communication as before.

(Means for Solving the Problems) In the present invention, a plurality of sets of telephones and data communication devices are connected via a common local area communication network. The telephones in each set are connected to one end of a common transmission line through a first low-pass filter, and the data communication devices are connected through a first high-pass filter. The other end of the transmission line is connected through a second low-pass filter to one terminal of the telephone exchange and through a second high-pass filter to one terminal of the folding device. The folding device has a function of outputting a signal input from one terminal to all remaining terminals.

(Function) According to the present invention, since the telephone/data exchange system is configured as described above, it functions as follows.

The signal from the telephone is sent to the shared transmission line at a low frequency by a first low pass filter.

On the other hand, the signal from the data communication device is sent to the shared transmission line at a high frequency by the first high-pass filter.

A second low pass filter connected to the other end of the shared transmission line passes only the signal from the telephone and supplies it to one terminal of the telephone exchange. On the other hand, the high-pass filter connected to the other end of the shared transmission line passes only the signal from the data communication device and supplies it to one terminal of the folding circuit. Telephone exchanges work like normal ones, with only one return circuit.
It serves to distribute the signals (packets) received from one data communication device to all other data communication devices, and the signals sent from the telephone exchange and loopback circuit follow the flow opposite to the above to each set of telephones. and data communication device, and only the designated telephone and data communication device accept the transferred signal. Since telephone communication and data communication are performed on the low frequency side and high frequency side, respectively, each communication can be performed independently, and the problems of the prior art described above are solved.

(Embodiments) Before describing embodiments of the present invention, a data communication system disclosed in Japanese Patent Laid-Open No. 58-64847 used in the present invention will be described.

FIG. 2 is a diagram showing the configuration of the above data communication system. In the figure, 11-in are data terminals, 21-2n are communication control devices, 41-4n are two-wire cables, and 5 is a folding device. Furthermore, the data terminals and communication control devices will be collectively referred to as data communication devices 31 to 3n.

In the system shown in FIG. 2, for example, terminal 11 is terminal 1n
The operation when sending data to is explained.

The communication control device 21 packetizes the data received from the terminal 11, adds the address of the communication control device 21 as a destination address, and sends it to the return device 5 via the two-wire cable 41. Since the loopback device 5 has a function of immediately looping back and outputting a packet input from one input terminal to the remaining terminal, in this example, the loopback device 5 divides and delivers the packet input from the cable 41 to the cables 42 to 4n. . The distributed packet is sent to the communication control devices 22 to 2n via each cable, the destination address is checked in each communication control device, and only the communication control device 21 having the corresponding address receives the packet. Put it in,
Transfer the data to the data terminal 11.

In order to avoid collisions between packets, the data communication device 31
~31n (that is, communication control devices 21~2n) do not transmit their own packets while receiving packets. However, if a plurality of data communication devices start transmitting packets at almost the same time, a packet collision occurs in the return device 5. In such a case, the return device 5 returns only the earliest arriving packet and does not accept the later arriving packet, thereby preventing both packets from being destroyed due to collision.

The technique described above makes it possible to perform both types of data exchange using a two-wire telephone line.

On the other hand, in order to perform telephone communication and data communication simultaneously and independently through a pair of transmission lines (2!! type telephone line), it is necessary to use some kind of multiplex transmission technique.

As a technique for this purpose, the frequency division method shown in FIG. 3 is suitable. In FIG. 3, 81 and Ei2 are low-pass filters, 71 and 72 are high-pass filters, and 8 is a transmission cable. If the passbands are sufficiently far apart and there is no mutual interference, between terminals A and A' and between terminals B and B'
Communication between them can be performed independently of each other.

If this frequency multiplexing transmission technology is used to perform telephone communication on the low frequency side, including direct current, and data communication on the high frequency side, telephone signals and data signals can be transmitted independently. Telephone signals include intermittent DC signals such as dial pulses, and such signals can be transmitted as is.

This invention realizes a combined telephone/data exchange system by combining the data exchange technology shown in FIG. 2 and the multiplex transmission technology shown in FIG. 3.

A combined telephone/data exchange system according to an embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 101-1On is a telephone, 111-1
1n is a data terminal, 211 to 21n are communication control devices, 3
11 to 31n are deaf data communication devices consisting of data terminals and communication control devices, 411 to 41n are two-wire cables, 6
11~81n, 821~Et2n are low pass filters, 711~? In, 721 to 72n are high-pass routers, 80 is a telephone exchange (PBX), and 90 is a return device.

In FIG. 1, signals from telephones 101-10n pass through corresponding low-pass filters 811-Bin, transmission lines 411-41n of the two-wire cable, and low-pass filters 821-B2n of the exchange, and are sent to the PBX 80. Connected. Since this signal has not undergone any processing such as modulation, P
In the BX80, it is treated exactly the same as a normal telephone number that does not go through a filter or the like.

On the other hand, the signals sent from the data communication devices 311 to 31n to the line side are filtered by high-pass filters 711 to 711? in, 721
72n and return device 90, and is transferred to the destination data terminal in the same manner as in the example of FIG. Since the signals sent and transferred here pass through a high-pass filter, codes with a large amount of DC components cannot be used. Therefore, in this embodiment, the code used on the data communication side is a code with a small DC component, such as the Manchester code (A) or the AMI code CB) illustrated in FIG. 4.

As described above, according to this embodiment, it is possible to carry out telephone communication as before by using transmission lines for telephone communication already installed in the premises, and also to perform data communication independently of telephone communication.

In the above embodiment, the telephone and the terminal are all configured as a pair, but only one can be connected if necessary. It is not necessary to install a filter for lines that connect only one side of telephone or data communication.

(Effects of the Invention) As explained above, according to the system of the present invention, by combining a frequency multiplexing circuit using a filter and a packet loopback device with a conventional telephone switching network centered on PBX, telephone A data complex exchange system can be easily realized.

Telephone and data communications are completely independent, so
It is possible to perform both at the same time or separately, and one communication does not affect the other, making it possible to perform telephone communication and data communication with good characteristics.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a diagram for explaining a data exchange method using a folding device, and Fig. 3
The figure is a diagram for explaining the frequency multiplexing transmission system, and FIG. 4 is a diagram showing an example of a data communication code. 101-Ion...Telephone, 111-11n...Data terminal, 211-21n...Communication control device, 311-31n...Data communication device, 411-41n
...2-wire cable, 811~Sin, Ei21~
G2n - low pass filter, 711-71n, 721
~? 2n-high pass filter, 80...telephone exchange, 90... loopback device.

Claims (1)

[Claims] A combined telephone and data switching system in a system in which multiple sets of telephones and data communication devices are connected via a common local area network to perform telephone and data communications, in which each set of telephones and data communication devices is It is connected to one end of one transmission line via a first low-pass filter and a first high-pass filter, and the other end of the transmission line is connected to a second low-pass filter and a second high-pass filter. A telephone connected to one terminal of a telephone exchange and one terminal of a return device through filters, and said return device having a function of outputting a signal input from one terminal to all remaining terminals.・Data complex exchange method.