Hello. I recently took a flight from LAX to STL, and we were sitting on the tarmac, due to the airport construction, we had boarded the aircraft in a much different way. Anyway, the forward cabin door had been shut for several minutes, and then was re-opened, and the pilots were in the cockpit pouring over what appeared to be flight manuals. The Captain then made an announcement that there was an equipment failure and they were waiting for an FAA mechanic to sign off on the flight so we could leave. The failure, according the the Captain, was in the Cockpit Voice Recorder. I have been searching, but, cannot find exactly what the rules are, but, apparently, flying without the CVR is permitted, as I would think at least the FDR was fine. However, being an avid armchair investigator, I was quite uncomfortable flying without a CVR, because, had the unthinkable happened, I know that one of the most critical pieces of information available to investigators is the CVR. How often do our commercial jetliners fly without this critical piece of equipment KNOWING it is not functioning? Would it have been required to ground the aircraft at the next stop to repair it, or would it have been permitted to finish it's duty day with a non-functioning CVR? Thanks in advance.