Hardy,
On our 767s that have the upgraded (744) RCPs and ACPs, whenever 121.500 is transferred to the active window, all ACPs automatically activate the selector (green light) of the VHF radio tuned to 121.500.
Basically, we always fly with VHF right tuned to 121.500, which forces all ACP VHF R green lights to turn on (we cannot manually deselect them, all we can do is turn the volume down, should we not want to listen to occasional superfluous chatter on the emergency frequency).
If we tune an ATIS (or any other frequency) on the right RCP, the automatic VHF R audio selection is disabled.
I wonder if this is just operator option or a permanent feature of this particular RCP/ACP model combination, regardless on type on which they are installed.
Perhaps 747 guys can chime in.
Best regards,
Mariano