Doorbell
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A doorbell is a signaling device typically placed near a door to a building's entrance. When a visitor presses a button, the bell rings inside the building, alerting the occupant to the presence of th
Doorbell at the entrance of Chetham's Library, Manchester, England
Doorbell mechanism from 1884 in Andrássy Avenue, Budapest
Antique mechanically operated shop doorbell on a torsion spring
Old door bell pull knobs in Edinburgh, United Kingdom. It is unclear whether bells were rung by wire and pulleys, or by electrical connection.
Buzzer
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A buzzer or beeper is an audio signaling device, which may be mechanical, electromechanical, or piezoelectric. Typical uses of buzzers and beepers include alarm devices, timers, train and confirmation
Piezoelectric disk beeper
Interior of a readymade loudspeaker, showing a piezoelectric-disk-beeper (With 3 electrodes ... including 1 feedback-electrode ( the central, small electrode joined with red wire in this photo), and an oscillator to self-drive the buzzer.