Which of the following is an example of an annunciator that uses vibration as the primary alert method?

The correct choice demonstrates the use of vibration as a primary alert method, which is characteristic of tactile devices. Tactile devices are designed to provide feedback through physical sensations, such as vibrations. This type of alert is particularly useful in environments where auditory or visual notifications may not be effective or accessible, like in noisy settings or for individuals with hearing impairments.

In contrast, other options listed serve different alerting mechanisms: horns produce auditory signals, visual strobe lights utilize flashing light to grab attention, and audio alert systems rely solely on sound. None of these options leverage vibration, which is the specific criterion that makes a tactile device the right choice in this context.