HT-503 PSTN Call Waiting

Does the HT503 support PSTN call waiting (and call waiting ID) on an active PSTN call?

That is, when the FXS (or VoIP port) is ALREADY on a PSTN call, and the FXO line is subscribed to call waiting (with ID) from telco, you hear the beep. Can the FXS port (or VoIP side) hook-flash the FXO line to answer the waiting call? (Can it also receive the PSTN call waiting ID?)

I have similar product which can't accomplish the above. If the 503 can, consider it purchased.

*PS, this is not the same as call waiting on the FXS port (on a VoIP call), with the FXO line idle.

Thanks.