US Patent 9117360 Low battery trouble signal delay in smoke detectors

The present invention provides a low battery trouble signal delay circuit for a smoke detector configured for periodically measuring environmental conditions and for producing a fire alarm signal when smoke is detected in the environment. The trouble signal delay circuit has a battery, a comparator configured for receiving a voltage measurement signal from the battery and a reference voltage measurement signal and sending a resulting signal to an activator circuit, at least one activator in the activator circuit that is user activated upon receiving a first input; and at least one low battery trouble signal annunciator connected to the activator circuit and configured for indicating that the voltage measurement signal is below the reference voltage measurement after receiving a signal from the comparator. The activator temporarily disables the low voltage trouble signal when activated for a silencing time period, while maintaining the operation of the fire alarm signal.