Videophone method and installation.

p0001The invention relates to the establishment of methods of communication in video telephony between a calling terminal and a called terminal via public or private networks and facilities for carrying out such a method and videophone terminals that they incorporate.

p0002It finds a particularly important application in telephone installations with videophones filtered through a telephone screening station, call the videophone to a number available for third parties, we will qualify for the sequel to "public", causing the orientation of the incoming call to telephone screening station.

p0003We will see that this installation architecture, where the filtering station is a phone and not a videophone, prohibits the establishment of communication on an incoming call from the network outside the periods when the filter is removed.

p0004firstly remind how normally establishes a call from a videophone videophone terminal, or calling for a called videophone. The calling subscriber presses the "videophone" from his terminal, as the number of the corresponding command and sending the call message. The videophone caller tries to establish a connection with a first LTCC channel (Communication System B transparent). If the call is accepted by the destination videophone, a second LTCC is established. The videophone communication can then take place, for example with use of H protocols 221. If the first transparent B channel can not be established, because the receiving station is not a videophone terminal but an ordinary telephone set, or if the second LTCC channel can not be established, the terminal starting videophone establishes a non-transparent channel NTBCC to fold in traditional telephony, having released the first LTCC if it had already been established.

p0005The called videophone terminal is filtered by telephone, we see that the calling videophone terminal can establish a videophone communication type and will fold in phone mode.

p0006The present invention aims in particular to provide a communication method for establishing videophone to a filtered set may be implemented requiring only very small changes in current videophone terminals. For this purpose, the invention proposes in particular a method of setting up a videophone communication from a calling videophone terminal to a called videophone terminal and filtered by a telephone set, characterized in that, once a telephone communication established between the terminals on a NTBCC channel is sent from the called terminal, a service message included in the line NTBCC release message containing a direct call secret number (unfiltered) of the called videophone and in that is restored directly from the calling terminal, a connection on two type B channels using the unfiltered call secret number.

p0007The secret remains unknown call number of the calling subscriber; it is simply stored in a buffer for the time necessary for the restoration of a videophone link. The availability for a single terminal two phone numbers, one of which is published involves no complication in networks comply with the latest recommendations of the CCITT, which allow multiple phone numbers under the term MSN (Multiple subscriber number).

p0008The invention also provides a telephone system for implementing the above method, comprising a videophone terminal assigned a public call number by the network and terminal filtering of telephone videophone, and means for towards filtering all incoming mail addressed to the public calling number,    characterized in that it comprises access means to call the videophone terminal without filtering, to a secret telephone number and means for transmitting, in response to a manual control of communication acceptance videophone, a message providing the secret address in calling videophone terminal.

p0009Videophone terminals with these features enable not only to implement the process defined above, but also more generally to pass, at the request of either of two visual telephone terminals already in telephone liaison, a conversation in telephone mode (on a non-transparent channel type CCNBT) to a videophone link via two channels LTCC.

p0010The method of the invention then comprises the following steps, once a type of bond telephony NTBCC a channel established between two videophone terminals: sending, from a first terminal, a NTBCC channel release message containing a service message with a direct appeal secret number of the first terminal and a call control instruction to establish, in return, a videophone communication on a first and a second LTCC channel automatic call from the second terminal videophone.

p0011The only changes to an existing type videophone terminal consist of:<ul><li>adding to launch the procedure for the videophone link, means for storing an additional service message and insert it into the line release message;</li><li>adding, to cause the establishment of the connection, means for identifying a request to establish communication and temporarily store the secret phone number that will be used in the procedure in substitution of public telephone number.</li></ul>

p0012The invention will be better understood on reading the following description of a particular embodiment given by way of nonlimiting example. The description refers to the accompanying drawings, wherein:<ul><li>Figure 1 schematically shows a call routing pattern from a calling videophone terminal V1 to a called videophone terminal V2 via a PBX PBX;</li><li>Figure 2 shows the sequence of operations that occur when videophone V1 of V2 video phone call to a filtered, causing a decline in phone mode;</li><li>Figure 3 shows the sequence of transfer operations of the call to the called videophone V2;</li><li>Figure 4 shows the operations during the release sequence of telephone communication and videophone communication facility.</li></ul>

p0013The invention will be exposed in its application to establish a communication from a calling videophone terminal V1 to V2 a videophone terminal filtered through a telephone filter mail, via a digital network integration ISDN service type and a PBX switchboard.

p0014It is assumed that the video phone calling a phone number or address # 4. The implementation of the invention requires that the called videophone terminal V2 is accessible to two addresses. One of the addresses or telephone number # 1 cause referral to the telephone call number filter # 3. A second call number, authorized by the features offered by recent and most PBX ISDN networks, provides access to videophone terminal without filtering. This second call number # 2 is secret, that is to say remains unknown to any requesting subscriber.

p0015Before describing the invention itself, will be recalled the sequence of operations involved in an existing installation of calling a videophone terminal filtered in a "public" address # 1 returned to a filtering station # 3. The sequence of operations is shown in Figure 1.

p0016The subscriber with the call number # 4 presses the "videophone" from his terminal, the address numbers of the # 1 requested party and presses the send key.

p0017There then attempt videophone mode connection with the V2 terminal. The V1 terminal sends the network a request handshake with V2, at # 1 on a transparent channel ISDN type of LTCC. The call is presented by the receiving switch not to V2 terminal, but the T2 post, LTCC mode, while it is ringing back. Lack of a response by the telephone T2 ago, after a delay and a new presentation of Appeal, LTCC release indicating the cause (non-response of the called terminal).

p0018After this sequence 1 (Figure 2), ended with the release of LTCC channel, the V1 video phone automatically launches a telephony connection method (Sequence 2 in Figure 2). This sequence includes a request handshake with the address terminal # 1, on a non-transparent channel NTBCC in telephony. The presentation of the call to the telephone filter T2, at # 3 is performed following the usual process and ends with the connection acknowledgment (ACK connection). There then passing conversation between the videophone terminal V1 and the telephone T2 filtering.

p0019Conventionally, the T2 station can transfer the call to the videophone V2, using the # 2 address that is not returned. The sequence until the passage in conversation between V1 and V2 is given in Figure 3. It is also conventional. There successively conversation between T2 and V2, in telephone mode, and call transfer to V2. At this point, the process of the invention allows one or other of the videophone terminals V1 and V2, to the extent that they are one and the other fully equipped, to substitute a videophone communication on two type B channels to the already established telephone communication.

p0020Figure 4 shows how is the return videophone mode initiative of the user of the terminal V2. The operations involve:<ul><li>breaking the established call,</li><li>sending a service message V2 to V1, giving the applicant's address "secret" unfiltered V2 terminal,</li><li>automatic videophone communication facility on two channels B.</li></ul>

p0021For this, the V2 terminal must have a memory of a service message which is incorporated in the release message of the telephone call.

p0022The establishment of the videophone communication sequence is caused by a recovery in demand for video calling, evidenced for example by pressing a button "videophone" V2. This request causes the disconnection and sending messages causing the release.

p0023Insofar as the videophone calling V1 is equipped with hardware and software enabling it to meet the service message, it makes a request for establishment of video call, but this time at # 2 that comes from he be given. The establishment of the connection can then be performed in the conventional manner between the unfiltered video phones, as shown in Figure 4. The final step of the sequence 4 is constituted by the establishment of the videophone link on a first TBCC channel. Once the first connection is established, there is establishment of a second LTCC channel (sequence 5).

p0024Note that once communication is established, the initiative of the videophone mode transfer can come from both the calling terminal behind # 4 that the terminal originally called. It is also noted that the establishment of the videophone communication can be made from not a videophone, but between two filter sets, then with establishing a telephone communication between the two videophones and videophone passage way .