[Billy] wanted to use the audio connector on his MacBook Pro for input and output at the same time. He knew it could be done because Apple sells headphones with built-in microphones that work with the computer. He set out to build a breakout box so that he could connect the components of his choice to the single port. Using a scart-RCA adaptor box he scrapped the scart plug and wired the RCA jacks to the Apple headphone wires. He can now patch the pickup of his guitar to the mic connector, send it through the MacBook, and run the output back to his guitar amp.