Like the HS810, the HS850 makes use of a body design that employs a folding microphone boom. The folding microphone boom acts as the on and off switch, as well as just providing a convenient way to make the headset smaller and more pocketable when not in use. When a call comes into your phone, you can turn on and answer the phone at the same time just by unfolding the microphone boom. You can end the call and turn it off by removing the headset and re-folding it. Using the headset in this way conserves battery power, since no battery juice is wasted on standby time - time where the headset sits around waiting to be contacted by a mobile phone or other compatible device. The physical design of the HS850 and the battery savings it imparts is my favorite aspect of the Motorola HS850.