Final answer:
Secondary power supplies must be capable of operating an Emergency Communication System in alarm mode for a set duration, often up to 12 hours at full load or equivalently at half-power over an extended period, as per the relevant safety codes.
Step-by-step explanation:
The question pertains to the required duration of operation for secondary power supplies for an Emergency Communication System (ECS) in an alarm condition. According to various safety and building codes, the secondary power supply should be capable of powering the ECS in alarm mode for a minimum duration to ensure safety and communication can be maintained during an emergency.
Considering scenarios where the system either operates continuously at full alarm load for a shorter period or at half-power for an extended period, both would need to provide equivalent levels of energy. Typically, for life safety systems, codes require a minimum operation of 24 hours in standby mode and 5 minutes of alarm operation. However, depending on the specific system and requirements, the precise duration at full load could be longer, such as up to 12 hours. It is important to consult current safety codes relevant to the location and type of ECS being used for the exact requirement.