JPH06152794A - Communication link forming method for isdn terminal equipment - Google Patents

Abstract

PURPOSE:To enable a single terminal equipment to surely acquire two B channels by transmitting continuously the flag signals of an HDLC frame onto a D channel for a period between the transmission of the 1st and 2nd call setting message. CONSTITUTION:A TV telephone system of the caller side continuously transmits the flag signals for a period between the transmission of the 1st call setting message 'SETUP' and the reception of an answer message 'CONN'. At the answering side, the flag signals are continuously transmitted for a period between the transmission of the message 'CONN' after reception of a call and the next reception of the message 'SETUP'. While a single terminal equipment is transmitting the flag signals of an HDLC frame onto a D channel, another terminal equipment set on the same circuit is unable to transmit various types of call control messages. Thus no outgoing/incoming is carried out any more. As a result, a signal terminal equipment can surely acquire two B channels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IS that connects to an ISDN by a basic interface and executes a call connection procedure twice during communication to form two B channel communication links.
The present invention relates to a communication link forming method for a DN terminal device.

[0002]

2. Description of the Related Art One ISDN basic line is provided with two B channels for information transmission. These two B channels can be used simultaneously by one terminal device. For example, by transmitting an audio signal on one B channel and transmitting a television image on the other, it is possible to perform videophone communication.

The CCITT recommendation defines specifications for forming two B-channel communication links in one call connection procedure. However, the current ISDN of each country does not yet support the communication function conforming to the specifications, and cannot be used by the user.

Therefore, conventionally, when two B channels are used for communication, a call connection procedure is executed twice between the communicating devices to form two B channel communication links. It was

By the way, a maximum of eight terminal devices are bus-connected to one ISDN line. Then, each terminal makes and receives a call as required and communicates using one normal B channel.

Therefore, one terminal device that uses two B channels executes the first call connection procedure and
After the communication link of the channel is formed, before the second call connection procedure is performed, another terminal device on the same line may make or receive a call first and the other B channel may be used. there were.

In this case, the one terminal device cannot use the two B channels at the same time, and cannot execute the predetermined communication.

[0008]

As described above, according to the conventional method,
There is a problem that one terminal device cannot surely acquire two B channels.

It is an object of the present invention to solve the above problems and provide a communication link forming method for an ISDN terminal device in which one terminal device can surely acquire two B channels.

[0010]

Therefore, in one invention of the present application, when one terminal device sends a call setup message twice to the other to form two B channel communication links, The terminal device continuously sends the flag signal of the HDLC frame on the D channel until the second call setup message is sent after the first call setup message is sent. Further, the other terminal device similarly continuously transmits the flag signal during the period from the reception of the first call setup message and the return of the response message until the reception of the second call setup message. .

According to another aspect of the present invention, one terminal device sends a call setup message to the other terminal, and then a call setup message is sent from the other terminal to one to form two B channel communication links. In addition, one terminal device,
After the call setup message is sent, the flag signal is continuously sent in the same manner as described above during the period until the call setup message is received from the other.

[0012]

When one terminal device is sending the flag signal of the HDLC frame on the D channel, another terminal device on the same line cannot send various call control messages, so that it cannot make or receive calls. As a result, one terminal device can surely acquire two B channels.

[0013]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 shows an ISDN according to an embodiment of the present invention.
Shows the terminal equipment of the subscriber of. In the figure, a videophone device 1 is connected to another terminal device 2 via an in-home bus 3 to an NT (line termination device) 4, and the NT 4 is
It is connected to ISDN.

In the videophone device 1, the handset 11 is for an operator to talk. The voice signal transmitting / receiving unit 12 converts a voice signal, which is an analog signal, into a digital signal and performs the reverse conversion. The communication control unit 13 executes call control using the D channel of ISDN and data transmission using the B channel in a predetermined procedure. The camera 14 captures an image of the operator. The display unit 15 displays the received image on the screen and displays the operating state of the device by a lamp. The operation unit 16 is used by an operator to perform various operations. The main control unit 17 is a microcomputer system that monitors and controls the above units. Memory 1
Reference numeral 8 stores the control program and other various data.

With the above configuration, the videophone device 1 of this embodiment uses two ISDN B channels at the same time to perform a call and an image exchange with a communication partner.

Next, the communication operation of the video telephone 1 will be described. For convenience of explanation, of the two devices communicating with each other, the one that makes the first call is called the calling side and the one that receives the call is called the responding side.

In the case of communication, the calling operator sets the other party in the videophone device 1 by a predetermined operation and activates it. Upon activation, the videophone device 1 on the calling side sends out a call setup message "SETUP" as shown in FIG.

By the way, such a call control message is an HDLC frame signal and is transmitted through the D channel. The HDLC frame signal is a "flag"
It is composed of fields of "address", "control", "information", and "frame check".

In the present embodiment, the calling side continuously sends the flag signal immediately after sending the call setup message "SETUP".

The ISDN sends its call setup message "SE
While sending "TUP" to the responding side, the call side responds with a call setting acceptance message "CALL PROC".

Upon receiving the call setup message "SETUP", the responding videophone device 1 starts ringing and calls the operator, and at the same time, sends out a call message "ALERT". The ISDN sends its call message "ALERT" to the caller. In FIG. 2, the call setting acceptance message “CALL PROC” is displayed.
In this expression, the sending of the flag signal is started after receiving the calling message "ALERT". However, while sending the flag signal, those messages are received at the same time.

On the responding side, the operator hears the ringing and operates the videophone device 1 to respond. When the videophone device 1 is operated to respond, the response message "CON
N "is sent. Immediately thereafter, similarly to the calling side, the flag signal is continuously transmitted.

ISDN sends its response message "CON
N "to the caller. This creates one B-channel communication link between the caller and the responder.

When the calling side receives the response message "CONN", the calling side stops the continuous sending of the flag signal. Then, the call setup message "SETUP" is sent to the same destination again.
Is sent. ISDN uses the call setup message "SE
While sending "TUP" to the responding side, the call setting acceptance message "CALL PROC" is returned to the calling side.

The responder receives the call setup message "SETU".
When receiving "P", a response message "CONN" is transmitted. The ISDN sends its response message "CONN" to the caller. This creates another B channel signaling link between the caller and the responder.

Here, the videophone device 1 on the calling side and the answering side starts predetermined communication. That is, an operator's voice transmitted from one handset 11 is transmitted to the other handset by one of the communication links and the other handset 11 is transmitted.
Output from. Further, the image captured by one camera 14 is transmitted to the other via the other communication link and is displayed on the screen of the other display unit 15.

After the communication is completed, the operator performs a predetermined ending operation. As a result, the calling side and the answering side execute the known call disconnection procedure twice to open the communication link and complete the above communication operation.

As described above, in the present embodiment, the video telephone apparatus 1 on the calling side receives the first call setting message “SET”.
After sending "UP", the flag signal is continuously sent for the period until the response message "CONN" is received. On the responding side, after receiving the call and transmitting the response message “CONN”, the call setting message “S
The flag signal is continuously transmitted during the period until "ETUP" is received.

Since the home bus 3 has only one D channel, when the videophone device 1 continuously sends a flag signal, the other terminal devices 2 cannot send a call control message during that period. Therefore, it does not make or receive calls. Therefore, during the call connection procedure of the videophone device 1,
The other terminal device 2 is prevented from using the other B channel. As a result, the videophone device 1 can surely acquire the two B channels and execute the predetermined communication.

In the above embodiment, the case where one videophone device 1 is installed on one line has been described as an example, but a plurality of videophone devices 1 may be installed. In that case, on the response side, a plurality of units simultaneously ring when receiving a call.
At this time, if the operator makes a response operation with any one, the operator can communicate with that one.

In the above embodiment, the response side sends the flag signal after sending the first reply message "CONN".
By sending the flag signal immediately after sending "T", it is possible to prevent another terminal device 2 from making or receiving a call during the period until the operator performs a response operation. However, in that case, only one videophone device 1 can be installed on one line.

FIG. 3 shows another embodiment of the call connection procedure. That is, in this embodiment, as in the above-described embodiments, the calling side continuously sends the flag signal after sending the call setup message "SETUP". Also, the responder is
When the operator receives the call setup message "SETUP" and calls the operator, and when the operator responds, the response message "CONN" is sent out. Thus, the first B
Form a communication link for the channel.

In the present embodiment, thereafter, the response side sends the call setup message "SETUP" to the calling side. ISD
N sends the call setup message "SETUP" to the calling side, while the call setup acceptance message "CAL" is sent to the answering side.
"L PROC". When the calling side receives the call setup message "SETUP", it stops sending the flag signal and sends a response message "CONN". Thus, a second B channel communication link is formed.

After that, a predetermined videophone communication is executed on the two B channels. Then, when the communication is completed, the calling side and the responding side execute the known call disconnection procedure twice,
Terminate the communication operation.

As described above, in this embodiment, the calling side first makes a call to form the communication link of the first B channel, and then the responding side makes a call and makes the communication of the second B channel. I try to form a link. In this way, even when both parties call each other, two communication links can be formed and predetermined communication can be executed.

On the calling side, the call setup message "S
After sending "ETUP", the flag signal is continuously sent for the period until the call setup message "SETUP" on the response side is received. This prevents the other terminal device 2 from using the other B channel during that period, and it is possible to reliably acquire two B channels.

In the above-mentioned embodiment, the television device is explained as an example, but the present invention can be similarly applied to various terminal devices which communicate by using two B channels at the same time. Since the television device is used by the operator, when the answering side receives the call setting message "SETUP", it waits for the operator's answering operation and then sends the answering message "CONN". In the case of the terminal device, it is natural that the response message "CONN" may be immediately transmitted when the call setup message "SETUP" is received.

[0039]

As described above, according to the present invention, one terminal device transmits the first call setup message,
Next, until the second call setup message is sent,
Alternatively, since the flag signal is continuously sent out on the D channel until the call setup message is received from the other terminal device, another terminal device on the same line is used by the other terminal device during those periods. Since the B channel is prevented from being used, two B channels can be surely acquired.

The other terminal device receives the first call setup message and returns a response message, and then 2
Since the flag signal is continuously transmitted until the second call setup message is received, it is possible to prevent the other B channel from being used by another terminal device, as described above. One B channel can be surely acquired.

[Brief description of drawings]

FIG. 1 is a block diagram of terminal equipment of an ISDN subscriber according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a call connection procedure between both communicating devices.

FIG. 3 is an explanatory diagram showing another embodiment of the call connection procedure between the two communicating devices.

[Explanation of symbols]

 1 Videophone Device 2 Other Terminal Device 3 Home Bus 4 NT 11 Handset 12 Audio Signal Transmitter / Receiver 13 Communication Controller 14 Camera 15 Display 16 Operation Unit 17 Main Controller 18 Memory

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 7/14 8943-5C

Claims (3)

[Claims] 1. An ISDN communication link forming method for forming a communication link of two B channels by sending a call setup message from one of two communicating terminal devices twice to the other, wherein one of the terminal devices is a first one. Method for forming a communication link in an ISDN terminal device, characterized in that the flag signal of the HDLC frame is continuously transmitted on the D channel during the period from the transmission of the second call setup message until the second transmission of the call setup message. . 2. The other of the terminal devices receives the first call setup message and returns a response message, and then 2
2. The communication link forming method for an ISDN terminal device according to claim 1, wherein the flag signal of the HDLC frame is continuously transmitted on the D channel until the reception of the call setting message for the second time. 3. An ISDN communication link forming a two B channel communication link by sending a call setup message from one of two communicating terminal devices to the other and subsequently sending a call setup message from the other to one. In the forming method,
One of the above terminal devices sends a call setup message,
A method for forming a communication link for an ISDN terminal device, wherein a flag signal of an HDLC frame is continuously transmitted on a D channel until the call setup message is received from the other side.