JP2003078932A - Telephone exchange system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system that can enhance a space efficiency for a large- scale telephone exchange and ensure speeches even on the occurrence of double failures. SOLUTION: A plurality of private branch exchanges for a small scale building are distributed and installed in a large scale building or a large scale area such as a large-scale factory, a regional developed city and an airport. The two small-sized exchanges 1, 2 are designated as center nodes A, B and the other small-sized exchanges 3, 4 are designated as decentralized nodes A, B respectively. Each of the center nodes A, B accommodate external lines of a public network 5. Further, each of the center nodes A, B and the decentralized nodes A, B is connected to two other nodes or more respectively. Extension terminals 6 are connected to each node. Moreover, in this embodiment, a central supervisory section 7 is installed in the small-sized exchange 1. Since each node implements live/dead supervision with each other, each node can quickly find out a defect. A redundant configuration is adopted for each node to avoid an entire area from being fallen into service interruption even when one node is out of order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone exchange system, which is commonly used in large-scale factories, regional urban development, large-scale buildings and regions such as airports, to exchange telephone lines between an outside line of a public network and a building extension line, and The present invention relates to a private telephone exchange system using a so-called PBX, such as telephone exchange between a building extension and a building extension.

[0002]

2. Description of the Related Art Conventionally, a large-scale factory, a regional urban development, a large-scale building such as an airport, and a local area telephone exchange system for an area are large in size and are directly wired from one exchange to each telephone. The installation space was large and the wiring efficiency was not good.

As one of the solutions, a system utilizing a remote switch in which a part of the concentrating function of the exchange is out has been developed. However, in the remote switch system, when a double failure occurs in the CPU and power supply of the node of the main body, the entire system does not operate.

For this reason, when high reliability is required, a highly reliable and high-cost central office switch for a first-class telecommunications carrier was installed.

[0005]

At present, the method of utilizing the communication path itself such as the Internet has changed drastically, and the private branch exchange system is not limited to the connection of the telephone, but the data communication utilizing the telephone line is carried out. The demand for line reliability is dramatically increasing. In addition, in large-scale factories, regional urban development, large-scale buildings such as airports and areas, it is required to introduce equipment with improved space efficiency in consideration of effective use of space.

While such needs are predicted, the conventional technology has the following problems. That is, since the conventional technology is constructed mainly of a large private branch telephone exchange, it is inefficient in space and has a sufficient redundant configuration, but when double failure or triple failure occurs, the entire area is cut off. There is a fear of becoming. In addition, large-scale private branch exchanges are often special devices, and there was room for consideration in terms of maintainability and price.

Therefore, an object of the present invention is to construct a private telephone exchange system having higher reliability by combining a plurality of private telephone exchange systems especially for small buildings.

[0008]

A telephone exchange system according to the present invention is a telephone exchange system shared by a large-scale facility, a group of facilities, or a wide area. A plurality of telephone exchanges constituting the system are distributed and arranged. In this way, a public line of a public telephone company is connected to each of the telephone exchanges distributed in a plurality of places, and the installed telephone terminals within the facility or facility group or wide area are distributedly connected to any of the telephone exchanges. 1) The telephone exchanges are connected to each other by a cable, and the cable includes a telephone line and a control signal line, or (2) the telephone exchanges are of a center node and a distributed node. And each node has a redundant configuration of a control unit and a power supply unit.

There are two types of telephone exchanges, one for the center node and the other for the distributed node. The center node telephone exchange and the distributed node telephone exchange monitor the life and death of the telephone exchange, and the control signal line performs this monitoring. It is preferable to control. Further, in the case where one of the telephone exchanges breaks down or goes down, it is effective in terms of safety to provide a mechanism for switching the outside line communication connecting from the exchange to the other public telephone exchange to go through another telephone exchange.

Further, it is preferable that a plurality of telephone exchanges, or each telephone exchange and the extension telephone of the control line are routed through an optical cable, or each of the telephone exchanges is provided with a dual modularized remote switch in a predetermined facility. It is desirable to dispersively connect with an optical cable and similarly connect a predetermined telephone to each of the telephone exchanges with an optical cable. The two-module modularized remote switch is effective for utilizing the line, and the modularized number is the PBX number.

[0011] Then, by adding a center and distributed nodes, it is possible to add a desired number of units, and further, when performing fault monitoring and / or billing monitoring, monitoring of a plurality of nodes is performed by a single integrated monitoring console. It is desirable to configure so that it can be carried out.

Further, when the present invention is applied to an airport in particular, one of the telephone exchanges is placed in the management building and the other one is placed in the airport terminal building, and the autonomous distributed multi-channel system is installed. It is effective to use a node private branch exchange system.

When the present invention is applied to an airport, it is desirable to install two PBXs in the center and two modularized remote switches in other areas to accommodate the subscribers of each area in two PBXs in a distributed manner. As will be understood, the center here has a function of bundling and receiving public lines and distributing them within their own management area (factory, facility, etc.).
Therefore, there is no upper limit to the number of PBXs distributed in the center, and in the case of an airport, the distribution destination may be outside the airport facility. Further, in the case of an airport facility, there are, for example, 30 or more buildings, but it does not matter if they are grouped by district instead of by building. There may be one PBX for each terminal building.

In the present specification, the telephone or extension terminal is a concept including terminals such as a computer terminal and a facsimile which are connected to a telephone line and use the telephone line. Also, "life or death" means to monitor this situation, with the death of the telephone exchange as "death".

When the remote switch is not used (such as a fueling center in an airport), subscribers in each district are distributed and accommodated in a plurality of PBXs. When the PBX goes down, even if the CPU dies and everything stops working, 2
Since it is heavy, it is usually okay, but safety is ensured by distributed storage.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of a telephone exchange system according to an embodiment of the present invention. In this example, a large-scale factory, a regional urban development, a large-scale building such as an airport, and a local telephone exchange for a plurality of small-scale buildings in the area (hereinafter referred to as "small-sized exchange").
That is) distributed. The two small exchanges 1 and 2 are positioned as center nodes A and B, respectively, and the other small exchanges 3 and 4 are positioned as distributed nodes A and B, respectively.

An external line of the public network 5 (= public line network; the same applies hereinafter) is accommodated in each of the center nodes A and B. Further, each of the center nodes A and B and the distributed nodes A and B respectively has two or more. In other words, in this example, the small switch 1 is connected to the small switches 2 to 4, the small switch 2 is connected to the small switches 1 and 3 and 4, and the small switch 3 is connected to the small switches 1, 2 and 4.
The small exchange 4 is connected to the small exchanges 1 to 3, respectively. In addition, extension terminals 6 are connected to each node (in the figure, four terminals each). Further, in this example, the integrated monitoring unit 7 is installed in the compact exchange 1.

Here, the integrated monitoring unit 7 is positioned as a console so that the live / dead state of each node can be visually observed. The installation location is not particularly limited, but the feature is that it can be viewed on one console. That is, there is no need to manage multiple exchanges with multiple consoles. In this example, one unit is installed, but it is also effective to make it portable and attach it to a failed node.

FIG. 2 shows an internal configuration example (block diagram) of each center node in FIG. As described above, the center nodes A and B are connected to the public network 5. On the other hand, the connection with the extension network 8 is shown, but this is a plurality of extension terminals 6
It is equivalent to a bundle of several. The center node is connected to the public network 5 by the public network I / F unit 9, is connected to the extension network 8 to the extension I / F unit 10, and is connected to other nodes by the control information I / F unit 11. Connected.

I / F is an abbreviation for interface.
Optical and metal cables will be inserted into this interface for both external and internal lines.

The public network I / F unit 9 is connected to the public network switching unit 12, the public network switching unit 12 is connected to the circuit switching unit 13,
The extension switching unit 14 is provided between the line switching unit 13 and the extension I / F unit 10. The control information I / F unit 11 is connected to the control unit 15, and the signal of the control unit 15 is configured to be output to the public network switching unit 12 and the circuit switching unit 13, respectively.
The control unit 15 includes a life-and-death monitoring unit 151 and a line control unit 152, and further includes a normal time table 153 and an abnormal time table 1.
54, monitoring information 155, and billing information 156 are attached.

The public network I / F unit 9 is a portion for connecting the public network to the exchange, and carries out wiring collection and wiring according to the type of the public network (optical cable, metal cable, etc.). Public network switching unit 1
Reference numeral 2 is a switch for switching an important public line to a normal exchange when the exchange fails. In response to an instruction from the control unit 15, the line switching unit 13 switches to connect to a designated telephone number destination in accordance with a caller's request. The extension switching unit 14 is a switch that switches an important extension to a normal exchange when the exchange fails. The extension I / F unit 10 is a portion for connecting the extension to the exchange, and carries out the wiring of the lines depending on the type of the extension (optical cable, metal cable, etc.). Control information I / F
The section 11 connects the exchanges in order to exchange the life-and-death monitoring information and the billing information exchanged between the exchanges. The control unit 15 is composed of the following two functions. The life-and-death monitoring unit 151 performs life-and-death monitoring of each exchange. Control information I /
The information of each exchange is acquired and managed through the F section 11.
The line control unit 152 controls the line switching unit 13 so as to connect to the designated telephone number destination in accordance with the caller's request.
The normal time table 153 has a control rule of the circuit switching unit 13 when each exchange is operating normally. Normally, the line control unit 152 executes control based on this table. The abnormal time table 154 has a control rule of the line switching unit 13 when any one of the exchanges fails. At the time of abnormality, the line control unit 152 executes control based on this table. The monitoring information 155 is a database that holds life / death monitoring information of each exchange. This function makes it possible to obtain information on all exchanges, regardless of which exchange the monitoring console is connected to. The billing information 156 is billing information of each exchange (telephone usage charges to tenants, etc.)
Is a database that holds. With this device, it is possible to obtain information on all exchanges by connecting the monitoring console of any exchange.

Similarly, the description of the distributed nodes A and B is given in FIG.
In the block diagram of FIG. 2, the control information I / F unit 16 is connected to other nodes, and the extension I / F unit 17 is connected to the extension network 8. The control information I / F unit 16 is connected to the control unit 18. The extension I / F unit 17 is connected to the extension switching unit 19, the line switching unit 19 is connected to the line switching unit 20, and the control unit 18 is configured to send a signal to the line switching unit 20. The control unit 18 includes a life / death monitoring unit 181 and a line birth / reception unit 182, and is provided with a normal time table 183, an abnormal time table 184, monitoring information 185, and charging information 186.

The line switching unit 20 switches to connect to a designated telephone number in accordance with a request from a telephone caller according to an instruction from the control unit 18. The extension switching unit 19 is a switch that switches an important extension to a normal exchange when the exchange is out of order. The extension I / F unit 17 is a portion for connecting the extension to the exchange, and carries out the wiring of the lines depending on the type of the extension (optical cable, metal cable, etc.). The control information I / F unit 16 is a port for connecting the exchanges in order to exchange the life-and-death monitoring information and the billing information exchanged between the exchanges. The control unit 18 has the following two functions. The life-and-death monitoring unit 181 carries out life-and-death monitoring of each exchange. The life / death monitoring information of each exchange is acquired and managed via the control information I / F unit 18. The line control unit 182 controls the line switching unit 20 so as to connect to the designated telephone number destination in accordance with the caller's request. The normal time table 183 has a control rule of the circuit switching unit 20 when each exchange is operating normally. Normally, the line control unit 182 executes control based on this table.
The abnormal time table 184 has a control rule of the circuit switching unit 20 when one of the exchanges fails. At the time of abnormality, the line control unit 182 performs control based on this table. The monitoring information 185 is a database that holds life-and-death monitoring information of each exchange. With this function, information on all exchanges can be obtained regardless of which exchange the monitoring console is connected to. The billing information 186 is a database that holds billing information of each exchange (such as billing of telephone usage charges to tenants). With this function, information on all exchanges can be obtained even if the monitoring console of any exchange is connected.

When a trouble occurs in one of the center nodes of the telephone exchange system according to the embodiment of FIG.
For simplification of description, a case where one center node goes down will be described with reference to the block diagram of FIG. 4 and the operation flow diagram of FIG.
In the figure, for convenience, the reference numerals of the respective elements of the center node B configuration are distinguished by attaching a ′ to the reference numeral of the corresponding center node A. The center nodes A and B perform mutual life-and-death monitoring by the life-and-death monitoring unit 151 (151 ') of the control unit 15 (15') (step ii after the starting step i in FIG. 5). If any node fails ("Yes" in decision step iii)
s "), controls the public network switching unit 12 (12 ') of the failed center node from the normal life-and-death monitoring unit 151 (151').
(Step iv), the important outside line is accommodated in the public network I / F unit 9 '(9) of the normal center node (in other words, among the outside lines of the public network, the important outside line is delivered to the normal node). : Step v). At this time, the control unit 1 of the normal center node
5 '(15) can be switched without using a telephone number or the like by using the abnormality table 154' (154). After this delivery, the integrated monitoring unit 7 is notified of the situation and the process ends (step vi → vii). Unless the failure is judged in the judgment step iii (that is, No), the life and death monitoring between the center nodes is continued. Basically, the monitoring information is obtained by connecting a console called an integrated monitoring unit to one of the exchanges.

Next, as to the measures to be taken when one of the distributed nodes goes down, FIG. 6 is a block diagram when trouble occurs in one distributed node of the telephone exchange system according to the embodiment of FIG. This will be described using 7. The distributed nodes A and B respectively perform mutual life-and-death monitoring by the life-and-death monitoring unit 181 (181 ') of the control unit 18 (18') (start step i-> step ii). If any of the nodes fails (Yes in step iii), the normal life / death monitoring unit 181 '(181) controls the extension switching unit 19 (19') of the failed distributed node (step iv) to set the important extension. It is accommodated in the extension I / F unit 17 '(17) of the normal distributed node (step v). At this time, the control unit 18 '(18) of the normal distributed node has the abnormal time table 184'.
By using (184), switching can be performed without changing the telephone number or the like. After the delivery in step v, the situation is notified to the integrated monitoring unit 7 and the process is completed (step vi → vi).
i). Incidentally, unless a failure is judged in the judgment step iii (that is, No), the life and death monitoring between the distributed nodes is continued. Even in the distributed node, it is sufficient to have one integrated monitoring unit 7 of the contact information in the system as described above.

Next, a block diagram when a trouble occurs in the center node in the telephone exchange system according to the embodiment of FIG. 1 will be described. When this embodiment is applied, in principle, as shown in FIG. An extension 6 (extension network 8) is arranged from a plurality of nodes in each department. By doing so, even if one node fails, the line can be secured from the other node. This is effective, for example, when all extensions of a department are not designated as important extensions. In the example of FIG. 8, when the circuit switching unit 13 of one center node goes down, the circuit switching unit 20 of one distributed node covers this.

In FIG. 9, a general (that is, conventional) remote switch system and the system of the embodiment of the present invention are image-wise compared and explained. The control unit 150 is installed in the center, and only the circuit switching units 13, 13 ', 20, 20' are distributed and installed.
Therefore, the number of accommodated lines is limited by the performance of the control unit 150. On the other hand, in the system of the embodiment of the present invention, since the control unit 15 (15 ', 18, 18') is provided in each node, the load of the control unit 150 can be distributed, and the number of accommodated lines is not limited.

Both of them have a circuit switching unit in the center. However, since there are extensions near the installation location of the exchange main body and these extensions can be switched by this circuit switching unit, the circuit switching unit is required. It is a thing.

As shown in the operation explanatory diagram of FIG. 10, the control unit 1 of each of the center nodes A and B and the distributed nodes A and B.
Monitoring information 155,15 in 5,15 ', 18,18'
Mutually manage 5 ', 185, 185'("cooperation" 2
1 to 23), management can be performed from one integrated monitoring console (= integrated monitoring unit 7) connected to any node or network. Therefore, management is not complicated even when a plurality of nodes are installed.

Further, as shown in the operation explanatory diagram of FIG. 11, the charging information 156, 15 in the control units 15, 15 ', 18, 18' of the center nodes A, B and the distributed nodes A, B, respectively.
6 ', 186, 186' are mutually managed ("cooperation" 2
1 to 23), management can be performed from one integrated monitoring console (= integrated monitoring unit 7) connected to any node or network. Therefore, management is not complicated even when a plurality of nodes are installed.

FIG. 12 shows an autonomous distributed multi-node private branch telephone exchange system in which the telephone exchange system of the present invention is applied to an airport. The switch 100 of the center node is the management building 2
Placed within 4. On the other hand, the switch 300 of the distributed node is placed in the airport terminal building 25. The public network 5 is ports 44 and 45 of the exchange 100 and port 5 of the exchange 300.
In addition to connecting to 2, 53, respectively, telephone terminal 3 outside the exchange
It is also directly connected to 0 and 31, and is wired so as to more reliably secure the communication line even in an emergency. These terminals 30 and 31 are also connected to the respective ports 39 and 47 of the corresponding exchanges 100 and 300, so that communication is normally performed through these exchanges. On the other hand, at the airport, in addition to these central buildings, facilities in a vast area,
There are areas. For example, a refueling center 57, a maintenance area 58, a firefighting facility, and facilities 5 of each affiliated company.
5,56. In this example, it is assumed that each facility 55, 56 and each area (for example, maintenance area 58, refueling center 57) are equipped with a plurality of remote switches or telephone terminals. For example, 2 of the remote switches in D facility 55
6 is connected to the exchange 100, and 27 is connected to the exchange 300.
Similarly, of the remote switches of the E facility 56, 28 is connected to the exchange 100 and 29 is connected to the exchange 300. Telephones 32 to 34 of the refueling center are appropriately connected to the exchanges 100 and 300 in a distributed manner. For example, 32 goes to exchange 100, 33 and 34
Will be connected to the exchange 300. Similarly, terminals 35 to 17 in the maintenance area are also distributed and connected to each telephone exchange. These extensions are ports 40 to 4 of the corresponding telephone exchanges, respectively.
3, 48-51. The wiring 38 is an optical fiber cable, and a telephone line and an information signal line are internally provided to connect the two exchanges.

According to each of the embodiments of the present invention described above, a private telephone exchange system shared by a large-scale building such as a large-scale factory, a regional urban development, an airport, etc., and a plurality of small-scale buildings. By installing the private branch exchanges for the building in a distributed manner, the cost, reliability, and maintainability are superior to the private branch exchanges for large-scale buildings. Then, since life and death monitoring is carried out by each node, the failure can be found promptly. In other words, by combining multiple private branch exchanges for small buildings, which are positioned as center nodes and distributed nodes, and each node has a redundant configuration, a system is constructed that does not disconnect all areas even if one node fails. In addition, by combining multiple private branch telephone exchanges for small buildings, the size of each exchange can be reduced to build a space-efficient system.

Further, it is preferable that, of the private branch exchanges for a plurality of small buildings, two or more are positioned as center nodes and the other are distributed nodes, and each node has a redundant configuration of a control unit and a power supply unit. Further, even if the center node has a double failure, the distributed node can operate alone, and even if the distributed node fails, it is possible to prevent the other nodes from being adversely affected.

An external line of the public network is connected to two or more center nodes.
If you pull in (for example, public telephone line, leased line, etc.),
According to the present invention, even when one node fails, half of the lines are secured by the other node, and the important one of the outside lines of the failed node (hereinafter referred to as “important outside line”) is automatically connected. It becomes possible to switch to a normal node and secure the line. Further, this mode can be realized without changing the telephone number by preparing two tables for normal time and abnormal time by each node and switching between them.

Next, by connecting the center node and the distributed nodes and between the distributed nodes, the important one of the extensions (hereinafter referred to as "important extension") is connected even when the distributed node fails. Automatically switch to a normal node,
It becomes possible to secure a line. Also, this aspect is
Each node prepares two tables for normal time and abnormal time, and by switching them, it is possible to realize without changing the telephone number.

Furthermore, if extension wiring is made from a plurality of nodes at the same installation location (department), even if one node fails, another node can secure a minimum line. Also, in the wiring method, the extension number can be freely given.

Further, by adding a center and a distributed node, it is possible to expand (expand) an unlimited number of lines, that is, by combining a private branch exchange for small buildings, the load is distributed to each control unit. by doing,
It is possible to eliminate the line limitation due to the processing capability of the control unit and to expand the number of lines without limitation.

Further, for example, between the center node and the distributed node,
By performing life-and-death monitoring between nodes such as between center nodes and distributed nodes, faults can be found quickly and fault information can be transferred immediately. In the fault monitoring function, monitoring of multiple nodes is integrated into one unit. Since it can be performed from the monitoring console, the billing functions can be integrated and billing for a plurality of nodes can be performed from one integrated monitoring console.

Further, according to the present invention, high reliability can be obtained. For example, the CP system (CPU) and the SP system (power supply) common control unit is completely duplexed, and the line system has an n + 1 configuration and reliability is enhanced. For example, the CPU and power supply are placed in each PBX. The number of lines will be one base. It should be noted that there has been no proposal to meet the needs of both reliability and scale. PBX can be a voice system that switches to the Internet protocol, but usually it can support about 2000 single lines (up to about 8000 lines) and a large building can usually do with this single unit, but it is like an airport or a large area. The present invention is particularly effective when it is required to have expandability.

In the above description, the PBX is used as the exchange.
VOIP is used instead of or in combination.
(Voice of IP = voice packet switch) is also an aspect of the present invention.

[0043]

As described above, according to the present invention, there is a private telephone exchange system shared by a large-scale building such as a large-scale factory, a regional urban development, an airport, and the area. By installing the exchanges in a distributed manner, the cost, reliability, and
It has excellent maintainability. Then, since life and death monitoring is carried out by each node, the failure can be found promptly.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a telephone exchange system according to an embodiment of the present invention.

FIG. 2 is a block diagram of a center node of the telephone exchange system according to the embodiment of FIG.

FIG. 3 is a block diagram of a distributed node of the telephone exchange system according to the embodiment of FIG.

FIG. 4 is a block diagram when a trouble occurs in one center node of the telephone exchange system according to the embodiment of FIG.

5 is an operation flow chart of the example of FIG. 4. FIG.

FIG. 6 is a block diagram when a trouble occurs in one distributed node of the telephone exchange system according to the embodiment of FIG.

FIG. 7 is an operation flowchart of the example of FIG.

FIG. 8 is a block diagram of the telephone exchange system according to the embodiment of FIG.
It is a block diagram when a trouble occurs in the center node.

FIG. 9 is an explanatory diagram for comparison with a remote switch system.

10 is an operation explanatory diagram of the embodiment system of FIG. 1. FIG.

FIG. 11 is an operational explanatory diagram of the embodiment system of FIG. 1;

FIG. 12 is an explanatory diagram of an example in which the example of FIG. 1 is applied to an airport.

[Explanation of symbols]

1-4: small exchange, 5 ... public network, 6 ... extension terminal, 7 ...
Integrated monitoring unit, 8 ... extension network, 9,9 '... public network I / F unit,
10, 17 ... Extension I / F section, 11, 16 ... Control information I /
F section, 12, 12 '... Public network switching section, 13, 13', 2
0, 20 '... Circuit switching unit, 14, 19 ... Extension switching unit, 1
5, 15 ', 18, 18', 150, 150 '... Control unit, 151, 151', 181, 181 '... Life / Death monitoring unit, 152, 152', 182, 182 '... Line control unit, 153, 153' , 183, 183 '... Normal table, 154, 154', 184, 184 '... Abnormal table, 155, 155', 185, 185 '... Monitoring information, 156, 156', 186, 186 '... Charging information,
24 ... Administration building, 25 ... Terminal building, 26-29 ... Remote switch, 30-37 ... Telephone terminal, 39-54 ...
Port, 100, 300 ... Switch, 38 ... Optical cable,
55, 56 ... Facility, 57 ... Refueling center, 58 ... Maintenance area.

Continued front page    (72) Inventor Yuichi Kitazume             4-6 Kanda Surugadai, Chiyoda-ku, Tokyo             Within Hitachi, Ltd. F term (reference) 5K049 AA07 AA09 BB04 BB21                 5K051 CC00 DD01 LL01 LL07

Claims (9)

[Claims] 1. A telephone exchange system shared by a large-scale facility, a group of facilities, or a wide area, wherein the telephone exchanges constituting this system are arranged in a plurality of distributions, and thus the telephone exchanges are distributed in a plurality of locations. A public line of a public telephone company is connected to each of the facilities or facility groups or installed telephone terminals in a wide area are dispersedly connected to any of the telephone exchanges, and the telephone exchanges are connected to each other by a cable. Is a telephone exchange system comprising a telephone line and a control signal line. 2. The telephone exchange according to claim 1, wherein there are a center node telephone switch and a distributed node telephone switch, and the center node telephone switch and the distributed node telephone switch are adapted to monitor whether the telephone switch is alive or dead. A telephone exchange system characterized in that the control signal line controls this monitoring. 3. The system according to claim 1, further comprising a mechanism for switching, when one of the telephone exchanges is out of order or down, external line communication connected from the exchange to a public line, through another telephone exchange. Characteristic telephone exchange system. 4. A telephone exchange system shared by a large-scale facility, a group of facilities, or a wide area, wherein the telephone exchanges constituting the system are distributed in a plurality of locations, and the telephone exchanges are distributed in a plurality of locations. A public line of a public telephone company is connected to each of the facilities or a group of facilities or a wide area installed telephone to each of the telephone exchanges, and the telephone exchanges include a center node and a distributed node. The telephone exchange system is characterized in that each node has a redundant configuration of a control unit and a power supply unit. 5. A telephone exchange system according to claim 4, wherein a plurality of telephone exchanges, and each telephone exchange and a control extension telephone, are routed via an optical cable. 6. The telephone switch according to any one of claims 1 to 5, wherein remote switches each of which is modularized in a predetermined facility are dispersedly connected by a duplicated optical cable to each of the telephone exchanges, and each of the telephone exchanges also has a predetermined telephone set. A telephone exchange system characterized by distributed connection with optical cables. 7. A telephone exchange system according to any one of claims 1 to 6, wherein a desired number can be added by adding a center and distributed nodes. 8. The system according to any one of claims 1 to 7, characterized in that, when performing fault monitoring and / or billing monitoring, a plurality of nodes can be monitored by a single integrated monitoring console. Telephone exchange system. 9. An autonomous vehicle at an airport, characterized in that one of the telephone exchanges according to any one of claims 1 to 8 is arranged in a management building and the other one is arranged in an airport terminal building. Distributed multi-node private branch exchange system.