I am a Sergeant heading over to Iraq. My XO wants me to create a circuit that enables us to hear our radio transmissions from our speaker box (24v, BN 123 connector - 6 pin), but when no transmissions are being heard, for us to listen to our music through our handheld player. I am trying to find a circuit diagram and/or parts list so I can create it. Any help would be great. Thanks ahead of time.