What specific alerting device uses visible signals to indicate events?

The use of flashing lights for fire alarms as an alerting device is particularly significant for individuals who are deaf or hard of hearing. These devices convert auditory signals into visual signals, effectively conveying important information through light. This is crucial in emergencies, where timely alerts can be the difference between safety and danger. Flashing light systems provide a clear and immediate notification of an event, such as a fire, allowing individuals to respond appropriately without relying on sound.

In contrast, the other options listed—hearing dogs, FM systems, and telecoils—serve different purposes. Hearing dogs are trained to alert their handlers to specific sounds, but they are not visual devices. FM systems enhance sound for individuals with hearing impairment but do not provide visual signals. Telecoils work with hearing aids to pick up sound directly from the environment, again focusing on auditory input rather than visible signals for alerting. Thus, flashing lights for fire alarms effectively fulfill the criterion of using visible signals to indicate events.