This would seem to signify that either the CVR and FDR have been separated or that one has stopped pinging.
Is there any way to differentiate which unit is radiating?
I doubt it.
Unless the two signals are modulated in some way I would say that they are identical. Besides, does it matter which unit is transmitting as long as one of them is found?
These pings were on 33.3 KHz rather than 37.5 KHz, which the pinger manufacturer says would account for drift due to low battery after 30 days active.
I would be very surprised if that were true. As battery life reduces it is the amplitude of the signal which will reduce, not the frequency.