Video-telephony system

1. A video-telephony system comprising:

a plurality of cameras, each capable of generating a video signal;

a plurality of display units which are able to receive video signals from the cameras via a wireless link;

a plurality of telephones which are able to communicate with each other;

means for identifying, based on the location of a first one of the telephones, a camera convenient for a user of that one of the telephones; and

means for transmitting a video signal generated by the camera to a display unit convenient for a user of a second one of the telephones engaged in a call with the first one of the telephones.

2. A video-telephony system as claimed in claim 1 , comprising a second camera convenient for the user of the second one of the telephones, and wherein the video signal from the second camera is transmitted to a display unit convenient for the user of the first one of the telephones.

3. A video-telephony system as claimed in either of claims 1 or 2 , wherein the cameras and the display units are wirelessly linked to the telephones so that a camera can communicate with a display unit via a telephone when the telephone is engaged in a call.

4. A video-telephony system as claimed in claim 1 , wherein the first one of the telephones comprises the said means for identifying.

5. A telephony system as claimed in claim 1 , wherein each telephone in the system comprises means for identifying a camera convenient for a user of the telephone.

6. A video-telephony system as claimed in claim 1 , wherein the camera convenient for a user is one which has in its field of view the telephone in use by the user.

7. A video-telephony system as claimed in claim 1 , wherein the means for identifying is arranged to identify as the camera convenient for a user a camera which, not already in use by a different user, is nearest to the telephone in use by the user.

8. A video-telephony system as claimed in claim 1 , wherein the display units are each integrated into a different one of the telephones.

9. A video-telephony system as claimed in claim 1 , wherein users of further ones of the telephones may also be engaged in the call.

10. The video-telephony system claimed in claim 9 , comprising means for transmitting video signals generated by cameras convenient to any users of further ones of the telephones to display units convenient for each other user engaged in the call.

11. A video-telephony system as claimed in claim 1 , wherein two or more calls can take place simultaneously within the system.

12. A video-telephony system as claimed in claim 1 , wherein each one of the cameras is capable of communicating with each of the telephones in the system via a wireless link.

13. A video-telephony system as claimed in claim 1 , wherein at least one of the cameras can adjust its field of view, or zoom in or out, according to a control signal from a telephone to which the camera is convenient.

14. A video-telephony system as claimed in claim 1 , wherein communication between two or more telephones is by a first protocol and communication between cameras and display units, or cameras and telephones, is by a different protocol.

15. A method for executing a call within a video-telephony system comprising a plurality of cameras, each capable of generating a video signal; a plurality of display units which are able to receive video signals from the cameras via a wireless link; and a plurality of telephones which are able to communicate with each other; the method comprising the steps of: identifying, based on the location of a first one of the telephones, a camera convenient for a user of said one of the telephones; and transmitting a video signal generated by the camera to a display unit convenient for a user of a second one of the telephones engaged in a call with the first one of the telephones.