Hi Richard,
It is possible to connect multiple cameras with the C40/C60/C90 and achieve the results you're looking for. You will be able to control the cameras which are daisy chained however, please keep in mind that you can only control one camera at a time which is set to be the Main Camera or Video Source.
So if you have 3 cameras connected, you can use them with the codecs and if Camera 1 is set to be the Main Video Source and you want to control the second camera, then you can switch the Main Video Source to Camera 2 and control it without any issues.
Daisy Chaining setup becomes much eaiser when using Camera Presets as using that, you dont need to make changes in the Main Source and you can define a number of presets for each camera and control them without issues.
Also the control is done via the VISCA control cable and HDMI is only used to carry the video and not control the camera. Here's a document available which explains the connections in detail:
http://www.cisco.com/en/US/docs/telepresence/endpoint/camera/precisionhd/user_guide/precisionhd_1080p-720p_camera_user_guide.pdf
Please refer to Chapter 5 on the following user guide.
Hope this answers your question.
Regards,
Mubashshir Akhtar
Thanks
Mubashshir Akhtar