On a 2a there's the "ring-o-lights". ISTR this is for a PIC connected to the output (only) of serial port 3, ie the serial on the back of the player.

The right code on the PIC and you've got 11 more outputs. You could put the right sort of header on any commands to prevent normal serial output getting misinterpreted too. Mainly though, you've got somewhere to solder the PIC down

Hugo