Features Compatible with all home and office telephones, two switches beside to be adjusted when necessary. Increasing Incoming volume 3 times (about 30dB), with an adjustable fingertip control. Perfect your hearing in noisy environments. Amplifies automatically when you lift the handset. Automatic Control Circuit minimizes levels of distortion. Connects between handset and phone base easily, no wiring involved. Light weight, compact and portable for travel. Use 2 standard AAA batteries. Powers automatically turn on/off to increase battery life. 1 year manufacturer's warranty provided. Packing Blister packing: 20pcs/CTN Carton Size: 40cm*30cm*17cm G.W.: 3KG