The Amplicom NL 100 Neckloop is a lightweight, easy to use accessory that plugs into your phone to give you enhanced audio. It's compatible with Amplicom PowerTel telephones and requires just one AAA alkaline battery (included). For hearing aid users the Amplicom NL 100 Neckloop can be set to the T position for clearer sound without interference. Integrated microphone. Battery status indicator. Includes 2.5mm to 3.5mm music player adapter.