I want to use my bluetooth headset (Sennheiser MB660 UC MS) with an app that doesn't support bluetooth
The MB 660 can be used in 3 different ways

Bluetooth: Here we are powered by ourself and handle NC using 3 microphones build in to the right earcup
USB: Here we offer the same performance as Bluetooth and could be used as an alternative for the customer smartphone
Analogue: Here we force OFF the Bluetooth and only drive the ANC circuitry for the speakers. Only the in-line omni dir microphone on the cable can be used for communications