JPH0685923A - Connection network changeover system - Google Patents

Abstract

PURPOSE:To call a subscriber in a network and to make a call to a subscriber outside of the network by providing a connection network changeover means selecting whether a private network is connected to a subscriber in the private network or a public network is connected to the subscriber based on a connection network changeover request signal to the system. CONSTITUTION:An exchange managing a public network in a software definition network(SDN) in which a subscriber optionally builds up a virtual private network by using the public network is provided with a discrimination means 1, a connection network changeover means 2, and a control means 3. Then the discrimination means 1 discriminates whether or not a caller subscriber is a subscriber in a private network and discriminates whether or not the caller subscriber sends a connection network changeover request. The connection network changeover means 2 selects whether a private network is connected to a subscriber in an optional private network or a public network is connected to the subscriber based on a connection network changeover request signal. The control means 3 controls the discrimination means 1 and the connection network changeover means 2. Thus, the call to the subscriber in the SDN group or in the public network is made by one terminal equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to telephone exchange technology, and particularly between subscribers in SDN (SOFTWARE DEFINED NETWORK) that enables subscribers to virtually construct a private network using a public network. Related to the communication line control method.

[0002]

2. Description of the Related Art Recently, with the progress of communication technology,
Various communication methods have been developed. Among them, the telephone exchange network is indispensable for the information-oriented society these days, and various exchange processes have become possible.

FIG. 10 is a schematic diagram showing the overall configuration of a conventional telephone switching network. The telephone exchange network is configured by connecting a plurality of exchanges connected to a plurality of subscriber terminals to a network.

In FIG. 1, the exchange 100 is connected to the subscriber terminal A1.
01 and the subscriber terminal B 102 are connected, while the exchange 200 has the subscriber terminal C (201) and the subscriber terminal D (20
2) is connected. And switch 100 and switch 200
Are connected via a network.

FIG. 11 is a diagram showing a connection form of lines in a conventional telephone switching network. In the figure, when the calling subscriber terminal A (101) goes off-hook, the exchange (100) detects this and transmits a dial tone signal to the subscriber terminal A (101). And the subscriber terminal A (101)
When the telephone number of the called subscriber terminal C (201) is dialed, the exchange (100) calls the exchange (200) that manages the called subscriber terminal C (201) based on this telephone number. It detects and makes a call request to the exchange (200). Then, the exchange (200) having received the call request transmits a call notification, that is, a ringing tone signal to the called-side subscriber terminal C (201). During transmission of this ringing tone, a ringing back tone signal is transmitted from the exchange (100) to the calling side subscriber terminal A (101).

When the called subscriber terminal C (201) responds to the call notification, that is, when the subscriber terminal C (201) goes off-hook, the exchange (2)
00) sets up a call line between the calling side subscriber terminal A (101) and the called side subscriber terminal C (201), and a call state is established between both subscribers.

After the call ends, the calling subscriber terminal A (101)
When is on-hook, both exchanges cancel the setting of the telephone line. In the above telephone exchange network, when the frequency of the number of calls between specific subscribers is high, it is complicated for the subscriber to dial the telephone number of the destination subscriber each time.
It was troublesome.

Therefore, conventionally, there has been known an SDN in which the subscriber can arbitrarily set a private network between at least two telephone terminals. SDN enables any subscriber to talk to another subscriber like an extension switching network.

For example, when the number of calls between the three parties is large, a private network is constructed between the three parties. At this time, a called number different from the called number in the public network is registered for each subscriber. When any subscriber makes a call to another subscriber, the calling subscriber can make a call to the subscriber in the private network by dialing only this called number. It will be possible.

FIG. 13 shows the overall configuration of a conventional switching network in SDN. In the exchange network, the exchange 100 and the exchange 200 are connected via the network.

The exchange 100 has the subscriber terminal A.
101 and the subscriber terminal B 102 are connected. On the other hand, a subscriber terminal C201 and a subscriber terminal D202 are connected to the exchange 200, an SDN group A is set up as a private network between the subscriber terminal A101 and the subscriber terminal C201, and a subscriber terminal B102 is connected. Subscriber terminal D2
SDN group B is set up as a private network with the network No. 02.

The exchange 100 and the exchange 200 are also provided.
Are connected to a common database 300. This database stores the called numbers in the public network corresponding to the called numbers in the private network (hereinafter abbreviated as SDN numbers).

The connection form of the lines in the SDN group will be described with reference to the sequence diagram of FIG. This figure shows a subscriber terminal A10 of the SDN group A in FIG.
2 is a processing sequence for making a call from 1 to the subscriber terminal C201.

First, when the subscriber terminal A 101 goes off-hook, the exchange 100 detects the off-hook and transmits a pulse dial tone indicating that the subscriber is in a state capable of connecting to the private network.

Upon recognizing the pulse dial tone, the subscriber terminal A 101 dials the called number (hereinafter abbreviated as SDN number) of the subscriber terminal C in the private network.

The exchange 100 which recognizes the SDN dial number accesses the database based on the SDN dial number, detects the called number of the subscriber terminal C201 in the public network, and joins based on the called number in the public network. The ringing tone signal is transmitted to the subscriber terminal C201 and the ringing back tone is transmitted to the subscriber terminal A101.

When the subscriber terminal C201 responds to the call request, the exchange 100 and the exchange 200 are connected.
Sets up a telephone line between the subscriber terminal A101 and the subscriber terminal C201.

After the end of the call, the exchange is the subscriber terminal A1.
Detects 01 on-hook and cancels the setting of the communication line. As described above, by arbitrarily reducing the number of digits of the SDN number, the complexity of the dial operation at the time of calling can be reduced, which is convenient.

[0019]

However, the above-mentioned SD
SDN different from any SDN group
SDN cannot be called to a group or to a subscriber outside the SDN group, that is, a subscriber in the public network.
The subscribers in the group need two telephone terminals, one for transmitting within the group and the other for transmitting to subscribers outside the group. Two telephone terminals are required depending on the call destination. It had to be used properly, and the operation was complicated and uneconomical.

Therefore, the present invention has been made in view of the above problems, and enables a subscriber in a private network to make a call to a subscriber in the same network and to a subscriber outside the network. It is an object to provide a technology for making a call.

[0021]

In order to solve the above-mentioned problems, the present invention is as follows. This will be described based on the principle diagram of FIG.

In a software-defined network in which a subscriber can arbitrarily construct a virtual private network using a public network, a discriminator 1, a connection network switching unit 2, and a control unit 3 are provided in an exchange managing the public network. Be prepared.

Here, the discrimination means 1 discriminates whether or not the calling side subscriber is a subscriber in the private network, and whether or not a connection network switching request is transmitted from the calling side subscriber. Is to determine.

The connection network switching means 2 switches whether to connect the private network or the public network to any subscriber in the private network based on the connection network switching request signal. The control means 3 controls the discrimination means 1 and the connection network switching means 2.

When the subscriber goes off-hook to the exchange, if the subscriber is able to connect to the private network, a first dial tone signal is transmitted to the exchange to establish connection to the public network. In this case, the dial tone transmitting means 4 for transmitting the second dial tone signal may be provided.

The discriminating means 1, the connection network switching means 2 and the control means 3 may be provided independently of the exchange.

[0027]

According to the present invention, when any subscriber goes off-hook, the control means recognizes this off-hook. And
The discrimination means discriminates whether or not the subscriber is a subscriber in the private network. Then, when the subscriber is a subscriber in the private network, the determining means determines whether or not the connection network switching signal is transmitted from the subscriber.

When the subscriber is a subscriber in the private network and the connection network switching request signal is transmitted, the connection network switching means connects the public network to the subscriber. As a result, the subscriber can make a call to the subscriber outside the private network by dialing an arbitrary called number.

On the other hand, when the connection network switching request signal is not transmitted from the subscriber, the connection network switching means connects the subscriber to the private network to which the subscriber belongs. In this case, the subscriber can make a call to the subscriber in the private network by dialing an arbitrary called number set in the private network.

When the exchange is provided with dial tone transmitting means, when any subscriber goes off-hook, the control means recognizes this and the discriminating means identifies the subscriber as a subscriber in the private network. It is determined whether or not there is.

When the subscriber is a subscriber in the private network, the dial tone transmitting means transmits the first dial tone to the subscriber. On the other hand, if the subscriber is not a subscriber in the private network, that is, if the subscriber is a public network subscriber, the dial tone transmitting means transmits the second dial tone signal to the subscriber.

Further, when the subscriber is a subscriber in the private network and has transmitted a connection network switching request signal, the dial tone transmitting means, after switching the connection network by the connection network switching means, performs the subscription. A second dial tone signal to the person. With this, the subscriber can determine whether the subscriber is in a connectable state with the private network or in a connectable state with the public network.

When any subscriber in the private network makes a call to a different subscriber in the private network, the connection network is switched to the public network by a connection network switching request, and the caller subscriber receives an incoming call in the public network. It is possible to make a call by dialing a number.

[0034]

EXAMPLES Specific examples of the present invention will be described below. FIG. 2 shows a schematic configuration of the SDN network in this embodiment.

In the figure, the SDN network is constructed by connecting a database 7 to a first exchange 6A and a second exchange 6B having different attributes. The first exchange 6A includes a subscriber terminal A (5A) and a subscriber terminal B (5
B) is connected to a subscriber terminal G (5G) and a subscriber terminal F (5F) in the public network.

On the other hand, the second exchange 6B has a subscriber terminal C (5C) and a subscriber terminal D (5D) in the SDN group.
And subscriber terminal H (5H) and subscriber terminal E in the public network
(5E) is connected.

In the present embodiment, the subscriber terminal A described above is used.
The first SDN group is set between (5A) and the subscriber terminal C (5C), and the subscriber terminal B (5B) is set.
The second SDN group is set between the subscriber terminal D (5D) and the subscriber terminal D (5D).

The database 7 includes a called number in the SDN network (hereinafter abbreviated as SDN number) for each subscriber terminal 5 in the SDN group and a called number in the public network (hereinafter referred to as SDN number) corresponding to each SDN number. The called number is abbreviated).

The exchange 6 is, for example, the first exchange 6A.
Receives a call request from the subscriber terminal A (5A) to the subscriber terminal C (5C), the SDN of the subscriber terminal B (5B) transmitted together with the call request from the subscriber terminal A (5A). The number is detected, and the database 7 is accessed based on this SDN number to detect the called number corresponding to the SDN number, that is, the called number of the subscriber terminal B (5B). Then, a call request is issued to the second exchange 6B, which is the exchange on the receiving side, based on the called number.

As a result, it is sufficient to dial an arbitrarily set SDN number from the subscriber terminal 5, and the operability is good. Next, FIG. 3 is a block diagram of the internal configuration of the exchange 6 in this embodiment.

The exchange 6 in this embodiment is provided with the discrimination unit 1
4, SDN group terminal registration table 8, control device 1
3, a connection network switching unit 9, an exchange function unit 10, and a dial tone transmission unit 12.

The discriminating unit 14 discriminates whether or not the arbitrary subscriber terminal 5 is an SDN group terminal. The SDN group terminal registration table 8 is for registering the SDN numbers of the subscriber terminals 5 belonging to the SDN group, and a detailed description thereof will be described later.

The connection network switching unit 9 switches the network to be connected to the subscriber terminal 5 in the SDN group from the SDN group network to the public network in response to a request from the subscriber terminal 5 in the SDN group.

The dial tone transmission unit 12 sends S to the subscriber terminal 5 which is in a state capable of connecting to the SDN group network.
The DN dial tone is transmitted, and the public network dial tone is transmitted to the subscriber terminal 5 which is in the state of being connectable to the public network.

The exchange function unit 10 performs switching processing of the communication line such as switching of the communication line and calling request processing. The control device 13 controls each of the above parts.

Next, FIG. 4 shows a concrete example of the SDN group terminal registration table 8 in this embodiment. In the SDN group terminal registration table 8 in this embodiment, the first SD
SDN belonging to each of the N group and the second SDN group
The called number within the SDN group of the subscriber terminal 5 in the group, that is, the SDN number and the terminal ID are registered.
When the discrimination unit 14 recognizes the telephone number of the arbitrary subscriber terminal 5, the discrimination unit 14 collates the telephone number with the SDN number registered in the SDN group terminal registration table 8 and, when both are coincident, the subscriber is concerned. The subscriber terminal 5 can be identified as a subscriber terminal within the SDN group.

The process of connection network switching control in this embodiment will be described below. FIG. 5 is a sequence diagram showing a connection network switching control process when the subscriber terminal 5 in the SDN group makes a call to the subscriber terminal 5 in the same SDN group.

The figure relates to a calling process from the subscriber terminal A (5A) belonging to the first SDN group to the subscriber terminal C (5C). First, when the subscriber terminal A (5A) goes off-hook, the first exchange 6A recognizes this and the first exchange 6
A identifies that the subscriber terminal A (5A) is a terminal within the SDN group, and transmits an SDN dial tone.

Then, the subscriber terminal A (5A), which has recognized the SDN dial tone, sends the call to the subscriber terminal C, which is the calling destination.
Dial the SDN number (5C). At this time, the first
The exchange 6A accesses the database 7 to access the S
The incoming call number of the subscriber terminal C (5C) is detected based on the DN number, and the second exchange 6B is notified of the outgoing call request based on this incoming call number.

The second exchange 6B recognizes the call request and transmits a ringing tone signal, and also transmits a ringing back tone signal to the subscriber terminal A (5A) via the first exchange 6A. .

Next, the subscriber terminal C (5
C) responds, the second exchange 6B determines that the subscriber terminal C
A call line is set between (5C) and the subscriber terminal A (5A) so that a call can be made between the subscriber terminals.

When the subscriber terminal A (5A) goes on-hook after the end of the call, the first exchange 6A which detects this goes to the second
The disconnection notification is sent to the exchange 6B, and the disconnection notification signal is transmitted from the second exchange 6B to the subscriber terminal C (5C).

FIG. 6 shows a calling processing sequence between subscriber terminals belonging to different SDN groups. The figure shows a subscriber terminal A (5A) belonging to the first SDN group.
To subscriber terminal D (5D) belonging to the second SDN group
Is a calling process for.

When the subscriber terminal A (5A) goes off-hook, the first exchange 6A that recognizes this goes to the subscriber terminal A (5A).
Identify that (5A) is a terminal within the SDN group,
An SDN dial tone is transmitted to the subscriber terminal A (5A).

Here, the subscriber terminal A (5A) transmits a connection network switching request signal, and the first exchange 6A switches the connection network of the subscriber terminal A (5A) from the first SDN group network to the public network. , Send a public network dial tone.

The subscriber terminal A (5A) recognizing the public network dial tone dials the called number of the subscriber terminal D (5D) which is the call destination. Then, the first exchange 6A
Based on this called number, the calling request is notified to the called second exchange 6B.

The second exchange 6B having received the call request transmits a ringing tone signal to the subscriber terminal D (5D), and at the same time, the subscriber terminal A is sent via the first exchange 6A.
The ringing back tone signal is transmitted to (5A).

Here, when the subscriber terminal D (5D) responds, the second exchange 6B sets up a communication line between the subscriber terminal A (5A) and the subscriber terminal D (5D). When the subscriber terminal A (5A) goes on-hook after the call ends, the first exchange 6A notifies the second exchange 6B of the disconnection, and the second exchange 6B
The exchange 6B transmits a disconnection notification signal to the subscriber terminal D (5D).

Next, FIG. 7 is a sequence diagram showing a calling process from the subscriber terminal in the SDN group to the subscriber terminal in the public network. This figure shows a process when a subscriber terminal A (5A) belonging to the first SDN group calls a subscriber terminal E (5E) in the public network.

When the subscriber terminal A (5A) goes off-hook, the first exchange 6A recognizes this and the subscriber terminal A (5A)
A) identifies that it is a terminal within the SDN group. Then, the SDN dial tone is transmitted to the subscriber terminal A (5A).

On the other hand, the subscriber terminal A (5A) which recognizes the SDN dial tone dials the connection network switching request signal. The first exchange 6A, which has recognized the connection network switching request signal, switches the connection network of the subscriber terminal A (5A) to the first S
The DN group network is switched to the public network and a public network dial tone is transmitted.

Subscriber terminal A (5A) recognizing that it is possible to connect to the public network by the public network dial tone.
Then, the called number of the subscriber terminal E (5E), which is the call destination, is dialed, and the first exchange 6A makes a call request to the second exchange 6B on the called side based on this called number.

The second exchange 6B, which has recognized the call request, transmits a ringing tone signal to the subscriber terminal E (5E) and, at the same time, sends the subscriber terminal A through the first exchange 6A.
The ringing back tone signal is transmitted to (5A).

Here, when the subscriber terminal E (5E) responds to the call request, a call line is set up between the subscriber terminal A (5A) and the subscriber terminal E (5E), and a call between both parties is made. Is started.

When the subscriber terminal A (5A) goes on-hook after the call ends, the first exchange 6A notifies the second exchange 6B of the disconnection, and the second exchange 6B notifies the subscriber terminal E (5).
A disconnection notification signal is transmitted to E).

The calling process from a subscriber in the public network to a subscriber in the SDN group will be described with reference to the sequence diagram of FIG. This figure shows a subscriber terminal F (5
F) relates to a calling process from the first SDN group subscriber terminal C (5C).

When the subscriber terminal F (5F) goes off-hook, the first exchange 6A recognizes this and the subscriber terminal F concerned.
It identifies that (5F) is not a terminal in the SDN group and transmits a public network dial tone signal to this subscriber terminal F (5F).

The subscriber terminal F (5F) that recognizes the public network dial tone dials the called number of the calling subscriber terminal C (5C). First exchange 6 based on this called number
At A, a call request is made to the second exchange 6B on the called side.

The second exchange 6B, which has received the call request, sends a ringing tone signal to the subscriber terminal C (5C) to notify the incoming call, and at the same time, the subscriber terminal A is sent via the first exchange 6A. A ringing back tone is transmitted to (5A) to notify that the subscriber terminal C (5C) is ringing.

In response to the call request, the subscriber terminal C (5
When C) responds, the second exchange 6B sets up a call line between the subscriber terminal C (5C) and the subscriber terminal F (5F) to start a call between the two.

After the call is completed, the first exchange 6A, which recognizes that the subscriber terminal F (5F) has gone on-hook, notifies the second exchange 6B of the disconnection, and the second exchange 6B receives the subscriber terminal C (5C). To the disconnection notification signal.

Next, FIG. 9 is a flow chart showing the operation process of the exchange in this embodiment. When the exchange 6 in this embodiment recognizes the off-hook of any subscriber terminal 5 connected to itself (step 901), the control device 13 detects the telephone number of this subscriber terminal 5 (step 902). The discrimination unit 14 discriminates whether the subscriber terminal 5 is an SDN group terminal or a public network terminal (step 903).
Accesses the SDN group terminal registration table 8,
By determining whether or not the telephone number is registered, it is determined whether or not the subscriber terminal 5 is an SDN group terminal.

In step 903, if the subscriber terminal 5 is an SDN group terminal, the dial tone transmitting unit 12 sends SD to the subscriber terminal 5.
The N dial tone signal is transmitted (step 904).

Here, the control device 13 determines whether or not the connection network switching request signal is transmitted from the subscriber terminal 5 (step 905), and when the connection network switching request signal is transmitted. The connection network switching unit 9 switches the connection network of the subscriber terminal 5 from the SDN group network to the public network (step 906), and the dial tone transmitting unit 12 transmits the public network dial tone signal (step 907).

Then, when the telephone number of the call destination is transmitted from the subscriber terminal 5, the control device 13 recognizes this (step 908) and makes a call request to the receiving side exchange (step 908). Step 909).

When the ringing tone signal is transmitted to the calling subscriber terminal, the exchange 6 transmits a ringing back tone signal to the subscriber terminal 5 (step 9).
10).

When the calling subscriber terminal responds to the calling request, a call line is set up between the subscriber terminal 5 and the calling subscriber terminal (step 911). In step 903 described above, the subscriber terminal 5 is SD
When it is determined that the terminal is not the terminal in the N group, the normal calling process using the public network is performed (step 91).
2).

Further, in step 905 described above,
If the connection terminal switching request signal is not transmitted from the subscriber terminal 5, the telephone number dialed by the subscriber terminal 5 is detected (step 913).

Here, the discriminating unit 14 refers to the SDN group terminal registration table 8 based on the telephone number, and determines whether or not the calling subscriber terminal belongs to the same SDN group as the subscriber terminal 5. It is determined (step 914). When the called subscriber terminal belongs to a different SDN group or is a terminal in the public network, the exchange 6 sends a warning sound to the subscriber terminal 5 to notify that the call cannot be made. (Step 917).

On the other hand, if the calling subscriber terminal and the subscriber terminal 5 belong to the same SDN group, the control device 1
3 accesses the database 7 based on the telephone number of the calling subscriber terminal and detects the called number of the calling subscriber terminal (step 918).

Based on the detected called number, the exchange function unit 10 requests the called exchange to make a call, and the following steps are the same as the steps 910 and thereafter. Therefore, according to the present embodiment, the subscriber belonging to the SDN group can perform both the SDN network communication and the public network communication with one terminal.

[0082]

According to the present invention, in the SDN network, it is possible to make a call from an arbitrary SDN group to a different SDN group or a call to a subscriber in the public network with one terminal. It is possible to simplify the operation and improve the economical efficiency.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a schematic configuration diagram of an SDN network in this embodiment.

FIG. 3 is an internal configuration block diagram of the exchange according to the present embodiment.

FIG. 4 is a specific example of an SDN group terminal registration table in this embodiment.

FIG. 5 is a sequence diagram showing a calling process between subscriber terminals in the same SDN group.

FIG. 6 is a sequence diagram showing calling processing between terminals in different SDN groups.

FIG. 7 is a sequence diagram showing a calling process from an SDN group subscriber terminal to a subscriber terminal in the public network.

FIG. 8 is a sequence diagram showing a calling process from a subscriber terminal in the public network to an arbitrary subscriber terminal in the SDN group.

FIG. 9 is a flowchart showing an operation process of the exchange in this embodiment.

FIG. 10 is a schematic block diagram showing the overall configuration of a conventional telephone switching network.

FIG. 11 is a sequence diagram showing a connection form in a conventional telephone switching network.

FIG. 12 is a schematic diagram of the entire configuration of a conventional SDN network.

FIG. 13 is a sequence diagram showing a connection form in a conventional SDN network.

[Explanation of symbols]

 1 ... Distinguishing means 2 ... Connection network switching means 3 ... Control means 4 ... Dial tone transmitting means 5 ... Subscriber terminal 5A ... Subscriber terminal A 5B ... Subscriber terminal B 5C ... Subscriber terminal C 5D ... subscriber terminal D 5E ... subscriber terminal 5E 5F ... subscriber terminal 5F 5G ... subscriber terminal 5G 5H ... subscriber terminal 5H 6 ... exchange 6A ... first exchange 6B ... 2 Switch 7 ... Database 8 ... SDN group terminal registration table 9 ... Connection network switching unit 10 ... Switch function unit 12 ... Dial tone transmission unit 13 ... Control device 14 ... Discrimination unit 100 ... Switch 101 ... Subscriber terminal A 102 subscriber terminal B 200 switch 201 subscriber terminal C 202 subscriber terminal D 300 database

Claims (2)

[Claims] 1. A software-defined network that allows a subscriber to arbitrarily construct a virtual private network using a public network, determines whether or not the subscriber is within the private network, and switches the connection network from the subscriber. Based on the connection network switching request signal, the determination means (1) for determining whether or not the request signal has been transmitted, and whether to connect the private network or the public network to any subscriber in the private network A connection network switching means (2) for switching and a control means (3) for controlling the above-mentioned respective parts are provided. When the control means (3) recognizes an off-hook of an arbitrary subscriber, the discrimination means (1) causes It is determined whether or not the subscriber is a subscriber in the private network, and if the subscriber is a subscriber in the private network, it is determined whether or not the connection network switching request signal is transmitted from the subscriber. , A connection network switching request signal is transmitted from the subscriber. Connection network switching means (2) connects the public network to the subscriber, and if the connection network switching request signal is not transmitted from the subscriber, the connection network switching means (2). (2) is a connection network switching system characterized by connecting a private network to the subscriber. 2. A dial for transmitting a first dial tone signal to a subscriber in a private network connectable state and a second dial tone signal to a subscriber in a public network connectable state. Tone transmitting means (4) is provided, and when the determining means (1) determines that the subscriber is in the private network connectable state, the dial tone transmitting means (4) notifies the subscriber. In response to the transmission of the first dial tone signal to the subscriber, and when the discriminating means (1) discriminates that the subscriber is in the public network connectable state, the second dial tone is sent to the subscriber. The connection network switching system according to claim 1, wherein a signal is transmitted.