In-Line-Amplifier 40Db with Tone ControlIn-line amplifier compatible with most home and office telephones, increases volume up to 40dB, adjustable tone selector, battery included, connects easily between handset and phone base. Mfg: Clarity. Mfg No: AMEHA40AM5. In-line-amplifier 40db with To Ame-ha-40. Phone Special Needs, Office, Business Services