The poster for SPARC has been sent for printing. The four little circles at the bottom are hopefully above where the buttons are on the sound playback card. I say "hopefully" as it hasn't arrived yet. I subsequently had to map their position using a little jpeg of it that I scaled up to what were listed as its dimensions.
I also decided not to label the buttons on the poster just in case disaster strikes and the audio device gets lost in the post. I can add some stickers to it later.