Designed for people with mild to severe hearing loss; Uses ClarityPower(TM) technology; Increases incoming sounds by up to 40dB; Adjustable tone control (600Hz-2.4kHz) amplifies specific frequency range for sound clarity & distinction between similar-sounding words like chair & share; Boost button allows for even more amplification & eliminates background noise & feedback by muting microphone in handset; Compatible with most home & office telephones where handset is separate from keypad; Easily connects between handset & phone base--no wiring involved; Compact & portable; Includes battery;