This Emergency Voice Communication System label has been designed to satisfy the requirements of the British Standards as described below:
BS 5839-9:2021 Clause 13.1f)2) states…
Every isolator and protective device that can isolate the supply to the EVC system, other than the main isolator for the building, should be labelled “EMERGENCY VOICE COMMUNICATION SYSTEM. DO NOT SWITCH OFF”, in the case of a switch (whether incorporating a protective device or not) that serves only the EVC circuit.