What is NOT a requirement for the secondary power source for household alarms?

The requirement for the secondary power source for household alarms is typically that it must be reliable and capable of functioning properly in case of a primary power failure. One of the essential aspects of this secondary power source is that it should be capable of causing audible trouble signals, ensuring that any issues with the alarm system are communicated effectively to the users. Additionally, the secondary power must be able to operate during an alarm condition for a set period, usually 4 minutes or longer, allowing the system to function briefly after the primary power is lost.

However, there is no specific mandate that the secondary power source must use rechargeable batteries. While rechargeable batteries can be an effective option, the requirement does not exclude other types of backup batteries, such as non-rechargeable batteries, provided they meet the necessary operational and performance criteria. Thus, stating that the secondary power source must exclusively use rechargeable batteries does not align with the actual requirement, making this the correct choice.