Answering machine functionality with 機能
Kanji Explanation: Ability and capability with 能

A murder suspect explains how when he called the victim, the phone kept ringing until the answering machine picked up.
- 目暮:
- 「奥
( さん!ここの留守番( 電話( の機能( は?」- “Ma'am! How does this answering machine function?”
- 奥
( さん: - 「は、はい… 十数回
( コールしても出( ない時( は、自動的( に留守番( 電話( に切( り替( わるようになってます…」- “Well... When there's no answer after ten rings, it automatically switches to the answering machine...”
機能
Key Points
機能
( here means function or operating behaviorMegure is asking how the answering machine system works.
In this scene 機能
( is about mechanism and operation, not usefulness in the abstract.