1. When the earphones are connected to two mobile devices, and neither device is in a call state: a) The earphones will output the ringing sound from the device that's receiving a call. 2. When the earphones are connected to two mobile devices and one of the devices is already in a call: a) If a call comes in on the non-calling mobile device, the earphones will play the incoming call alert, and the earphone buttons will prioritise controlling the incoming call device. If the earphones hang up the current call, the audio channel will switch to the incoming call on the other device. Note: Please refer to the product instructions on the official CMF website or get in touch with our Customer Support.