impossible to accept a ringing call while in another call

I was on a call today when another participant called me. While I could hear the ringtone and was asked for permissions to use the camera/microphone, I couldn't see any popup asking me to accept/refuse the call. The entire screen was displaying a video (with overlay hangup/mute controls) but the pop up did not show up. I had to hang up and call again to stop the ringtone.

Is multi-participant a supported feature?

I'm using firefox 29 on osx.

Multi-participant is technically possible (rooms) but not supported by the UI at the moment. For now, I'll set the user as "busy" when in a call and reply automatically to the caller with a chat message, similar to what happens when you reject a call. What do you think? I'll give some thought to the multi-participant support...

Yep, that works, thanks.