JPH0227858A - Call transfer control system between exchange stations - Google Patents

Abstract

PURPOSE:To utilize a communication line effectively in call transfer by attaining the discrimination as to whether plural communication lines are used duplicatedly by one and same transfer call between a relay exchange network and an called exchange station applying transfer operation by means of a common line signal. CONSTITUTION:In the case of call transfer processing by a called exchange station 1, the called exchange station 1 uses a common line signal to an adjacent relay exchange station so as to identify whether or not the communication line used for the communication of the caller exchange station and the communication line used for the communication with a transfer destination exchange station exist between the same stations. When it is available, a relay connection request is sent to a relay exchange network constituting the relay exchange stations through a link 40. Thus, an interruption request of the communication line 30 not required in the transfer of a call from the adjacent relay station to the called exchange station is sent to the called exchange station via the link 40 and the unrequired line forming the connection route is used efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a switched communication system, and more specifically to a call transfer control method between exchanges in a switched communication system.

(Prior Art) There are forward routing methods and rerouting methods as methods for controlling call transfer between exchanges.

These include, for example, rccITT Red Book No. 7.

0 described in Signaling System Specification Recommendation 0784J When the called terminal performs a call transfer operation and the call is forwarded using the forward routing method, the originating exchange center that was used before the transfer, The connection route between the relay switching center and the destination switching center is used as is, and a new connection route to the transfer destination is formed from the destination switching center via the relay switching center. Thus, in forward routing, calls are routed through the terminating switch.

In addition, when the called terminal performs a call transfer operation and the call is transferred using the rerouting method, the connection with the originating switching center, relay switching center, and terminating switching center that was used before the transfer will be changed. Among the routes, those that are unnecessary for the connection route between the originating switching center and the transfer destination switching center are disconnected. The call is then transferred by forming a new connection route between the one originating switching center and the transfer destination switching center.

(Problem to be Solved by the Invention) In this way, in the forward routing method, the initially set connection route with the destination switching center is used as is, so a single call, for example, can be made between the same relay stations. A disadvantage is that multiple connection routes may be used, and the communication lines forming the connection routes are not used efficiently. Furthermore, in the rerouting system, if the originating switching center and the relay switching center exchange call control signals using the individual line signaling system, a new connection route cannot be formed between the originating switching center and the transfer destination switching center. Therefore, the call is transferred through a connection route similar to the forward routing method. Therefore, in this case as well, the efficiency of the communication line cannot be improved as in the forward routing method.

Furthermore, in the rerouting system, there is a problem in that the blocking rate is higher in the acquisition of communication lines between offices than in the acquisition of connection paths within the exchange, and that transfer routes cannot be easily formed.

The present invention overcomes these drawbacks of the prior art, makes it possible to efficiently use the communication lines forming the connection route, and is applicable even when an individual line signaling system is included between the originating switching center and its relay switching center. The purpose of this system is to provide a call transfer control system between switching centers.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides switching in a switching communication network constituted by a relay switching center network having a plurality of subscriber line switching centers and at least one relay switching center. In the inter-office call transfer control method, a first subscriber terminal accommodated in a first subscriber line switching center is transferred to a second subscriber terminal accommodated in a second subscriber line switching center via a relay switching center network. connected to subscriber terminals,
When the second subscriber terminal performs a transfer operation to connect the first subscriber terminal to a third subscriber terminal accommodated in a third subscriber line switching center, the relay switching center network When making a relay connection between a subscriber line exchange and a third subscriber line exchange, the third subscriber line exchange that is connectable among the relay exchanges connected to the first subscriber line exchange A connection route is formed within the relay exchange near the central office, and the second subscriber line exchange releases the line connected to the relay exchange network, and further connects the relay exchange that is no longer needed within the relay exchange network. Release the connection line between.

(Function) According to the present invention, the first subscriber terminal accommodated in the first subscriber line switching center and the second subscriber terminal accommodated in the second subscriber line switching center are connected via the relay switching center network. When the second subscriber terminal is connected to the second subscriber terminal, the second subscriber terminal connects the first subscriber terminal to the third subscriber terminal accommodated in the third subscriber line switching center. When the transfer process is performed, when the first subscriber line switching center and the third subscriber line switching center are relay-connected by the relay switching center network, the relay connected to the first subscriber line switching center A connection route is formed within the relay exchange that is closest to the third subscriber line exchange among the exchanges, and the relay exchange network is connected to the second subscriber line exchange that is no longer needed due to call transfer. The connecting lines are released, and the connecting lines between the relay exchanges that are no longer needed in the relay switching center network are also released.

(Embodiment) Next, an embodiment of the inter-switching center call transfer control system according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a basic configuration diagram of a common channel signaling switching center which is advantageously applied to the call transfer control system between switching centers according to the present invention. For example, it separates the functions of voice calls and exchange connection signals,
An exchange that controls connections between exchanges by sending and receiving exchange connection signals over a dedicated common line.

The exchange 1 is a subscriber line exchange that can accommodate a plurality of subscriber terminals, such as telephones 2, or a relay exchange that does not accommodate any subscriber terminals. Trunk 5 is a trunk of exchange 1 that transmits and receives voice signals across exchanges. The trunk 5 is connected, for example, to trunks 5 of neighboring stations of the preceding and succeeding stations via a communication line 30. The connection path 60 is a connection path that connects within the exchange 1, and the communication control device 7 that connects between the trunks 5 within the exchange 1, between the telephone 2 and the trunk 5, or between the telephones 2, connects between the exchanges 1 and 2. This is a device for exchanging exchange connection signals, and is connected to the exchange 1 via a control line 100. The control device 7 is connected to the communication control devices 7 of the preceding and succeeding adjacent stations in the same way as the speech trunk 5 via a common line signal link 40 for transmitting and receiving exchange connection signals.

When the telephone set 2 is connected between exchanges 1, an exchange connection signal is sent to and received from the other exchanges 1 via the signal link 4G. As a result, a connection route for one call line 30 is established, and a call can be made between the accommodated telephone 2 in the local exchange 1 and a desired accommodated telephone 2 in the other exchange. exchange l
When making a relay connection, it connects the calling trunk 5 on the calling side and the calling trunk 5 on the called side via the connection path 60, and also transmits the exchange connection signal received from the calling side adjacent station to the called side neighboring station. Send.

When the destination switching center 1 performs call transfer processing, the destination switching center 1
check whether the call line used for calls to the originating exchange and the call line used for calls to the transfer destination exchange exist between the same exchanges using a common line signal to the adjacent transit exchange. Identifies and links relay connection request if possible 40
The information is then sent to the relay switching center network that constitutes these relay switching centers.

As a result, a request to disconnect the communication line 30 that is no longer needed for call transfer from a relay station adjacent to the destination switching center is sent to the link 40.
The call line 30 is sent to the receiving exchange via the call center, and the unnecessary call line 30 is disconnected.

2 to 4 show relay system diagrams of a communication network constituted by an exchange 1. In FIG. Exchanges IA, IB and I
D corresponds to the exchange 1 shown in FIG. 1 which functions as a subscriber line exchange, and an extension telephone II corresponds to the extension telephone 2.
&2a, 2b and 2d are accommodated as subscriber terminals. In the relay switching center network IC, the switching center 1 functioning as a relay switching center is, for example, a hierarchical communication network.0 Call lines 30a, 30b, and 30d correspond to the call line 30,
These lines transmit voice signals between exchanges IA, IB, and 10 and exchange network IC. Signal links 40a, 40c, 40
d corresponds to the signal link 40, and the exchanges IA, IB, 1
This is a control signal line for exchanging exchange connection signals between 0 and the exchange network IC. Further, a speech line 30e and a signal link 40e are wired between the exchange IA and the exchange 10. Furthermore, the relay connection link 80 shown in FIG.
is a call link connected within the transit exchange network IC.

Referring to FIGS. 2 to 4, a relay system for call transfer control in this embodiment will be described when the telephone 2a makes a call to the telephone 2b, and after the connection is completed, the telephone 2b performs a transfer process to the telephone 2d. In the relay system diagram of FIG. 2, the connection state during a call between the calling side telephone 2a and the called side telephone 2b is shown by a thick line. Using the figure, the operation from when telephone 2a and telephone 2b are connected until a telephone conversation can be made will be explained.

When telephone 2a sends out a selection signal for telephone 2b, exchange IA sends this selection signal as an exchange connection signal to relay switching network IC via signal link 40a. When the relay exchange network IC receives the connection signal, the relay stations in the relay exchange network IC sequentially select optimal routes, and the connection route with the destination exchange IB that accommodates the telephone 2b is determined. As a result, the call lines are captured one after another, and the telephone 2 shown in bold line in the figure
a-Switching center IA-Telephone line 30a-Relay switching center network IC-
A call is made between the calling side telephone 4112a and the called side telephone 2b through the connection route of the telephone line 30b, the switching center IB, and the telephone 2b.

In the relay system diagram of FIG. 3, a connection state in which the receiving side telephone 2b puts the calling side telephone 2a on hold and is negotiating with the telephone 2d is shown by a thick line. Using the same figure, telephone 2
The operation up to a meeting between telephone 2d and telephone 2d will be explained. When the telephone 2b performs an operation for making a meeting call with the transfer destination telephone 2d, the exchange IB connects the telephone line 30b connected to the telephone 2a to the hold tone trunk 5b. As a result, the hold tone is sent to the telephone set 2a. Also, the selection signal of the meeting optical telephone 2d is transmitted to the signal link 4.
0c to the switching network IC, and a connection route with the transfer destination switching center ID is established via a relay station within the switching network IC. As a result, a connection route of telephone 2b--speech line 30c--exchange network IC--speech line 30d-exchange ID--telephone 2d is formed, and a meeting is held between the receiving telephone 2b and the meeting optical telephone 2d.

In the relay system diagram of FIG. 4, a connection state in which the calling side telephone 2a is connected to the transfer destination telephone 2d as a result of the receiving side telephone 2b performing a transfer operation is shown by a thick line. After the meeting between telephone 112b and telephone 2d is completed, telephone 2b
When the terminating exchange IB performs a transfer operation, the destination exchange IB checks whether relay connection is possible between the adjacent relay exchange of the originating exchange IA and the adjacent relay exchange of the transfer destination exchange 10 via the connection link 40c. The determination is made by receiving information from the network IC. Then, when relay connection is possible, destination switching center IB sends information to the effect that relay connection is possible to switching center network IC via signal link 40c.

When the relay exchange network IC receives the relay connection enable information, a relay connection link 80 is formed by the relay exchange. As a result, the originating exchange IA and the transfer destination exchange 10 are connected, and the originating telephone 2a - call line 30a - relay connection link 80 - call line 30d - exchange ID - transfer destination telephone 2
The telephone 2a is transferred to the telephone 2d through the connection route d. In addition, in order to release the communication lines 30b and 3Qc between the destination switching center IB and the relay switching center network IC, which are no longer needed during call transfer, the relay switching center network IC sends the disconnection request signal to the destination side via the signal link 40c. Send to exchange IB. Upon receiving this disconnection request signal, destination switching center IB releases speech lines 30a and 30b.

Note that if the relay connection link 80 cannot be formed within the relay switching center network tC, a message indicating that a relay connection will be made within the destination switching center 1B from the relay switching center network IC to the destination switching center IB via the signal link 40c. When the destination exchange 1B that sends the request receives this request signal, it transfers the originating phone fi2a to the forwarding destination phone 2d by making a relay connection within the own exchange log 1B.
Connect to.

In this way, the signal link 4 is established between the exchange IB and the exchange network IC.
If the terminating exchange IB is able to send and receive exchange connection signals associated with transfer processing with the relay switching network IC, the terminating exchange IB of the forwarding destination telephone 412d will be connected via 0G. Can be connected to ID.

This includes, for example, the originating exchange IA and the relay exchange network IC.
This is possible even when relay connections are made between stations using the individual line signaling system.

The relay method diagram in FIG. 5 shows the connection route after transfer in the forward routing method according to the prior art when the first called side type talk machine 2b performs the transfer operation. As shown in the figure, when a call is transferred using the forward routing method, the call is transferred via one terminating exchange 50b, so a single call may involve multiple communication lines between the same stations. There is a problem that one call line is not used efficiently.

The prior art also includes a rerouting method as a call transfer method. This is done by adding a new telephone line 30e between the originating exchange 50A and the transfer destination exchange 500, and cutting off unnecessary telephone lines between the originating exchange 50A and the terminating exchange 50B. Achieves call forwarding. Therefore, in the case of the rerouting method, the originating switching center 50
This is applicable only when the relay switching center connected to the switching center A and the switching center 50A of the relay switching center network 50G performs relaying between the switching centers using a common line signaling system. If the relay exchange network 50
If the switching center 50A of G and the relay switching center connected to it use the individual signaling system, the call transfer is performed by a connection route similar to the forward routing method shown in FIG. Another problem is that the rerouting method has a high blocking rate and makes it difficult to supplement call lines.

In contrast, in this embodiment, it is possible to determine whether a plurality of call lines 30 are connected between the relay exchange network IC and the destination exchange IB by the same transfer call. For this reason, 1. It is possible to establish a relay connection between the originating exchange IA and the transfer destination exchange 10 through the relay exchange network IC without going through the destination exchange IB that performed the transfer operation. Therefore, the speech line 30 can be used effectively in transferring calls, and the blocking rate during transfer is almost the same as in normal relay connections.

Note that in this embodiment, the telephone 2b of the destination exchange IB performed the transfer operation, but the present invention is not limited thereto; for example, the telephone 2a of the originating exchange IA performed the transfer operation to the telephone 2d. also has the same effect as described above.

(Effects of the Invention) According to the present invention, multiple communication lines are used redundantly for the same transfer call between the relay exchange network and the destination exchange that performed the transfer operation using common line signals. It becomes possible to determine whether the Therefore, if a plurality of call lines are used redundantly for the same transfer call, unnecessary call lines can be released by making relay connections within the relay exchange network. Therefore, it is possible to effectively utilize the telephone line in transferring calls.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a common line signaling switching center applied to an embodiment of the call transfer control method between switching centers according to the present invention, and FIGS. 2 to 4 are call transfer according to the present invention. 5 is a relay system diagram showing a relay system for control. FIG. 5 is a relay system diagram showing a relay system for call transfer control according to the prior art. l. 2. 5. 7. 30゜40゜Part 1 Switching center telephone call trunk communication control device call line signal link

Claims (1)

[Scope of Claims] A call transfer control method between switching centers in a switching communication network constituted by a plurality of subscriber line switching centers and a relay switching center network having at least one relay switching center. A first subscriber terminal accommodated in a first subscriber line switching center is connected to a second subscriber terminal accommodated in a second subscriber line switching center via the relay switching center network. and when the second subscriber terminal performs a transfer operation to connect the first subscriber terminal to a third subscriber terminal accommodated in a third subscriber line switching center, the relay switching center network When making a relay connection between the first subscriber line switching center and the third subscriber line switching center, the third subscriber line switching center that can be connected to the first subscriber line switching center is the
A connection route is formed within a relay switching center close to a second subscriber line switching center, and the second subscriber line switching center releases the line connected to the relay switching center network. Call transfer control method.