Sennheiser VMX Office Bluetooth Headset Unique speaker - Perfect Sennheiser quality sound guaranteed. Multi switch - To switch the headset on/off, to adjust volume level, to mute microphone during a call, to cancel or ignore a call. Hook switch - To take and end the call, or toggle between calls from office phone and mobile. Can be used to activate voice dialling and redial of last number if phone supports these features. Infinite talk time - Use of second exchangeable battery gives infinite talk time, as one battery reloads while the other is in use. Headset status - LED shows headset status: Standby; out of range; busy/online; battery low and incoming call.