Class Change Signal in Fire Alarm Systems Explained

Class change is a non-fire signalling mode used in schools and certain other occupied buildings, where the fire alarm system is briefly used to sound a distinctive tone or chime over the same notification network at the end of each lesson period.

The class change signal is operated either from a dedicated key-switch on the panel, from a programmed time schedule, or from a separate input device. The key constraint is that it must be plainly distinguishable from the actual fire alarm tone or voice message, both in pattern and in duration. Typical implementations use a short two-tone chime or a short steady tone of a few seconds, never the slow-whoop or temporal-three pattern reserved for evacuation.

Class change is permitted in many UK and Irish schools because it avoids installing a parallel public-address system. The compromise is that staff and pupils hear the fire alarm sounders many times each day, which can erode response if the implementation is sloppy. A well-designed scheme uses a clearly different tone, a short duration, and ideally a parallel visual indication so that no one is left guessing whether to evacuate.

The signal is configured in the panel's cause-and-effect rather than wired separately. For the wider notification context, see fire alarm fundamentals. For voice-based alternatives that avoid the dual-purpose ambiguity, see voice alarm systems.