it with the telrphone line, other electric power is needed. It helps the hearing-impaired, the heavy sleepers, and people who love wandering far from their phones. This product is made with superior electronic ,designed by high technology. It has preety appearance,stable function,loud and clear sound,suitable for using in the noisy places. QUALITY GUARANTEE: Best quality. Our Brand is dedicated to provide high standard products，we have confidence in our products and provide after sale support,if you have products quality issues, please contact us.