4th Class Power Engineering 4A9 Practice Test 2026 - Free Power Engineering Practice Questions and Study Guide

In a PLC (Programmable Logic Controller) with an HMI (Human-Machine Interface), signaling an alarm can occur through various methods, and one effective means is by operating a beacon. Beacons are visual indicators often used in industrial settings to provide a clear signal of an alarm condition, which can be easily seen from a distance. This method helps to ensure that operators are immediately aware of potential issues, enhancing safety and response times.

While other options, like changing the color of the HMI screen or sounding an alarm sound through a siren, can also be effective ways to signal alarms, each has its own context of use. For example, the change of screen color is primarily a visual cue that might be missed if an operator is not focused on the screen. Similarly, sounding a siren might not always be the feasible or preferred method, as it can create noise pollution or be disregarded in a crowded environment.

The action of flashing an equipment icon on the HMI can certainly grab attention, but it relies heavily on the operator monitoring the display, which might not always be the case. Operating a beacon combines visual presence with potential mobility constraints, ensuring that anyone in the vicinity is alerted to the alarm condition, making it a widely accepted practice