What is the function of the comb plate switch on an escalator, and what actions does it initiate when activated?

The comb plate switch on an escalator is a safety device located at both the top and bottom landings of the escalator, where the moving steps transition into a stationary comb plate. The comb plate is a toothed metal plate that aligns with the grooves in the escalator steps, allowing passengers to smoothly step on or off the moving escalator. The primary function of the comb plate switch is to detect obstructions or foreign objects that may become lodged between the moving steps and the stationary comb plate. This is a critical safety feature, as such obstructions can create a tripping hazard or cause damage to the escalator. The comb plate switch is typically a mechanical switch that is activated when the comb plate is deflected or displaced by an obstruction. The switch is connected to the escalator's control system, and when the switch is activated, it immediately initiates a series of actions to ensure safety. The first action is to stop the escalator. The control system immediately cuts power to the escalator's drive motor, bringing the escalator to a halt. This prevents the obstruction from causing further damage or injury. The second action is to activate an audible alarm. The alarm alerts passengers to the stopped escalator and the potential hazard. This allows passengers to safely step off the escalator and avoid tripping. The third action is to prevent the escalator from restarting automatically. The control system requires a manual reset by a qualified technician before the escalator can be restarted. This ensures that the obstruction has been removed and the escalator is safe to operate. In some escalators, the activation of the comb plate switch may also trigger a visual indicator, such as a flashing light, to further alert passengers to the stopped escalator. By quickly detecting obstructions and initiating these safety actions, the comb plate switch plays a vital role in preventing accidents and ensuring the safe operation of escalators.