If the speaker is connected via Bluetooth:
• Please go to the list of devices available for Bluetooth connection and switch the device to treVolo U.
If the speaker is connected with an audio cable:
• Mac or tablet: Sound > Input > Switch to External Microphone
• Windows PC: Audio Setting > Input > Switch to Headset
• If you are connecting with a desktop, it's unlikely to support a 4-pin earphone connector, so treVolo U cannot connect your desktop with an audio cable.
• The microphone built into treVolo U is highly sensitive, please do not use from a short distance (<5cm). Excessive volume may activate the protection mechanism and cause the microphone to go silent. If this happens, you can unplug and re-plug the 3.5mm headphone jack on your personal device.