Ringer That Lets an Occupant Know You Have Arrived

Puzzle 3 of Secondhand Treasures Pack

Question is: Ringer That Lets an Occupant Know You Have Arrived

and the answer is: DOORBELL

Word Meaning:

DOORBELL — A bell, buzzer, or chime device mounted on or adjacent to a door's exterior, meant to be rung by a visitor to announce one's presence.

Definitions from Wiktionary.