In-Line telephone sound amplifier with a strobe light that amplifies ringer volume from the corded telephone for the hearing-impaired to recognize the incoming call! The extra loud ringer helps the hearing-impaired, the heavy sleepers, and people who love wandering far from their phones hear the incoming calls. The strobe light allows people with severe hearing impairment to see the indication for incoming calls! —made with a high-quality plastic material that can also sustain drops and minor accidental damage. NOTE: Not compatible with cellular phones. Ultra-bright flashing light alerts you of incoming calls in quiet environments. Works with any home phone. No battery is needed. Connects directly to the telephone and the telephone line. It comes with an extra loud ringer (95 dB) and volume control (Hi/Low) controller to easily adjust the intensity. Simple to use and install!