If you’ve read our review of the third-generation iPod shuffle and editorial on its remote control authentication chip yesterday, you already know that while the EFF was concerned about “DRM” in the chip, our concern was different:

“If you want a pair of headphones that will work to control the new iPod shuffle, you will now have to buy something that Apple either makes itself, or approves—this process has already led to needlessly overpriced video cables and chargers, as well as creating problems for many additional types of accessories that you may or may not have ever heard of.”

A source provided us with some additional insider details on the remote chip that might interest those of you who wanted to know more specifics on what’s going on here.

Internally, Apple has been referring to the chip as a transmitter chip; it is technically a dual-mode modulator that overlays remote control commands on top of the headphone or microphone signal, coupled with a controller in the iPod. According to Apple’s own documentation, the chip gets power from the iPod, then transmits encoded control information to the iPod, which has a controller that receives and decodes the button information. Using the chip, Apple’s microphone-equipped versions of the headset operate in either “button mode” or “tone mode,” sending control commands either as differing voltage levels or as ultrasonic tones ranging from 99 to 300kHz.

This source suggests that the chip can be seen in a positive or negative light. On the positive side, it provides developers access to a new part that Apple could have kept for itself and its own products. On the negative side, to get the chip, a developer is required to sign Apple’s Made For iPod agreement, which has serious consequences: first, Apple must issue its approval in advance for each specific remote controlled headphone product; only afterwards will the developer will be given access to the chips. Next, there are the other MFI issues—the contract (think App Store contract, multiplied), royalties on some product sales, monthly accounting reporting to Apple, and audits, amongst them. All this for an in-line remote control.

These details will be linked to yesterday’s editorial and the original review.

Jeremy Horwitz

Jeremy Horwitz was the Editor-in-Chief at iLounge. He has written over 5,000 articles and reviews for the website and is one of the most respected members of the Apple media. Horwitz has been following Apple since the release of the original iPod in 2001. He was one of the first reviewers to receive a pre-release unit of the device, and his review helped put iLounge on the map as a go-to source for Apple news.