Works in either mode It works in two modes, noise reduction state or common headset state. When battery runs out, it still works on common state. LONG BATTERY LIFE Rechargeable Long-lasting Li-Ion Battery provides up to 20 hours of continuous use. Never worry about being out of battery power! the headphones can operate without battery power (with noise cancelling turned off) PORTABLE CONVENIENCE Easy to take with you: Foldable design in combination with the included travel case provide a highly portable listening solution. Free your time ACTIVE NOISE CANCELLING HEADPHONES WITH MICROPHONE-Long long travel will not be boring and noisy any more,enjoy the movie ,music ,radio and so on. Devotion on work Internal precision noise reduction circuitry effectively eliminates up to 85% of background noise . More focus on your job , without being disturbed even in the noisy background EXTREME COMFORT Full cover earmuff design,inside use imported inert sponge,soft&comfortable,long time wear without geting tired. Compact and Lightweight Weight only 0.4lb, lighter than iPhone 6s Plus,20% lighter than any other on ear headphones on the market. They're so lightweight you'll forget you have them on!