connecting 2 or more cameras in Onyx

[franc]

hi,
I'm running Onyx 4.2.1 on a 64bit 10.10 Ubuntu laptop...
I want to connect several cameras for a live performance and i was
just experimenting with a second webcam other than my in regular
webcam on the laptop monitor...
Onyx is not recognizing the other usb webcam i'm trying to connect...
i've tried messing around with the settings.xml and with the
default.xml but i'm not even sure of what they do ...
the camera works, i'm sure... (it's /dev/video1) and i opened it in
VLC.
Is it possible to make Onyx detect other cameras?
Help me if you can...
Many thanks

Franc