These Apple earphones are a bit of an anomaly. The design is based upon its Apple Earphones with Remote and Mic that was sold independently and also included with the iPhone 3GS, iPhone 4, iPhone 4s, and iPod touch (Generation 3). Each of those devices used a microphone. At the same time, Apple released the iPod Shuffle Generation 3 that did not have microphone compatibility. Instead of using an old earphones design, they instead produced the same design without a microphone.
This version of the Apple Earphones with Remote and Mic without a Mic lacks the small Mic hole in the housing on the right-ear wire. Previous Apple Earphone designs lacked the + and – volume controls and the microphone on models that included the Mic.
Of course, I would love to tear these apart or X-ray them to see if Apple left out the microphone, or simply covered the microphone hole in this version of the earphones.
Sources: Apple, Apple (via webarchive)
