Studio Six Digital has been producing custom hardware for the iOS platform since iPhone 3GS, in 2009. Some items were discontinued because the iOS devices would no longer support them, and others were superseded with improved designs.

iAudioInterface – The original iPhone interface connected to the device with a 30-pin connector, and used analog audio I/O. Apple deprecated analog audio from the 30-pin port with iPhone 5, so these devices are not useful today.

iAudioInterface2 30-pin – The original iAudioInterface2 used a 30-pin hardwired cable. This device is not upgradeable to use with Lightning or USB C devices.

iTestMic – This design was updated and improved, to add an audio output port and support iOS device charging, with iTestMic2.

uTestMic – This model used a A-type USB connector, and was replaced with the iTestMic2 with USB C.

See the links below for more information.