How do sound and light alarms effectively warn during elevator bypass operation using specific sound and flash frequencies?
Publish Time: 2025-10-08
During elevator maintenance, inspection, or emergency rescue operations, technicians often need to activate "bypass" mode—temporarily bypassing some safety circuits and causing the elevator to operate at a lower speed under abnormal conditions. While necessary, this operation significantly increases the risk of accidental startup, occupant entrapment, and even shearing accidents. To ensure safety, national standards mandate that elevators activate a dedicated sound and light alarm during bypass operation. This alarm is typically installed at the bottom of the car. Using scientifically designed sound and flash frequencies, it provides a clear, unmistakable warning signal to personnel inside and outside the hoistway, becoming a key line of defense against accidents.1. Audio Design: Penetrating Noise to Trigger an AlarmThe audio signal of a sound and light alarm is not randomly generated; it is carefully considered based on both human factors engineering and safety regulations. This frequency range coincides with the human ear's highest sensitivity in noisy environments, effectively penetrating motor noise in the machine room, hoistway reverberation, and background noise. The alarm uses an intermittent "beep-beep-beep" or continuous pulse tone, rather than a monotonous, long beep, to prevent omissions due to auditory fatigue. The sound pressure level is typically no less than 85 decibels, ensuring clear hearing within a range of 10 meters. This highly recognizable sound pattern quickly alerts maintenance personnel, nearby workers, and even building personnel, signaling, "The elevator is operating abnormally. Keep out of the way."2. Flashing Frequency: Strong Visual Cue, Adaptable to Complex Lighting ConditionsSynchronized with the sound, the alarm features a high-brightness LED flashlight, typically red or yellow. Red is used internationally to represent "prohibition" and "danger" in safety signs, while yellow offers high visibility, especially in dimly lit shafts. The flashing frequency is strictly controlled within 1–2 Hz, avoiding both rapid flashes that could cause visual blur and slow flashes that could be mistaken for ordinary indicator lights. This frequency matches the human persistence of vision, creating a strong flashing sensation in peripheral vision. Even maintenance personnel with their back to the elevator car or high up in the shaft can detect abnormal conditions through reflected light or peripheral vision. Some high-end models also feature dual-side or circular lighting designs to expand viewing angles and eliminate blind spots.3. Installation Location and Interlocking Logic Ensure Accurate WarningsThe alarm is installed at the bottom of the elevator car, offering two advantages: First, it is close to the maintenance personnel's regular work area, ensuring that the warning signal is received immediately; second, it is protected from obstruction by equipment or decorations on the car ceiling, ensuring unimpeded transmission of sound and light. Its triggering logic is deeply integrated with the elevator control system: the alarm automatically activates only when the "bypass switch" is physically activated and the elevator enters maintenance or emergency operation mode; the alarm stops immediately once the bypass is released. This "state binding" mechanism eliminates false or missed alarms, ensuring accurate and authoritative warnings.In summary, the sound and light alarm for elevator bypass operation, through its scientifically designed sound frequency, flashing frequency, installation location, and interlocking logic, creates an efficient, reliable, and ergonomically designed safety warning barrier. It is not only a compliance requirement but also a technological embodiment of responsibility for life, silently safeguarding the safety bottom line of every maintenance operation.
