Sennheiser models (like the Urbanite, MOMENTUM and certain ear buds) with a control and microphone integrated into the cable are often offered in two variants ... the "i" variant (for Apple devices) and the "g" variant (for Android devices). NOTE: The headphones (regardless of the variant) will plug into an audio device and provide audio and only the control and microphone functionality is affected by the device/variant.
The "i" variant is wired specifically for Apple devices that are 3rd generation and later. The "i" variant will only have full microphone and control functionality when connected to Apple devices.
The "g" variant is wired specifically for Android devices that utilize the Android wiring configuration that allows for control functionality. The "g" variant will only have full microphone and control functionality when connected to Android devices utilizing the control functionality wiring configuration.
NOTE: For some Android models (particularly older Android models) that do not follow the control functionality wiring configuration then the functionality of the controls would be limited.
Please check the device/model compatibility here: (http://senncom.com/comm/home_en.nsf/compatibility.html?ReadForm&lang=EN&brand=HTC&model=8X). NOTE: If the model is not listed in this compatibility guide then functionality of the controls is likely to be limited.