also: ラインアダプタ
noun
line adapter
A device that adapts a telephone line or network line for connection to other equipment. Common in telecommunications and networking contexts.
このラインアダプターを使えば、アナログ電話をデジタル回線に接続できます。
Using this line adapter, you can connect an analog telephone to a digital line.
Borrowed from English 'line adapter'.