Smoke detector including an indicator for indicating a missing primary

Abstract

A smoke detector having an audible missing primary power source indicator, capable of indicating the absence of a primary power source powering the detector is provided. A missing power source circuit, including a supplementary power source having an effective voltage below a predetermined reference value is connected in parallel with the primary power source of the smoke detector. Additionally, the smoke detector contains low voltage detection and alarm circuitry, connected to the primary and supplementary power sources, to produce an audible warning when the effective voltage powering the smoke detector is determined to be below a predetermined reference value. Primary power to the detector may be supplied by a DC battery, a DC power source which has been converted from AC power or by a combination of the two. In one embodiment of the present detector, the supplementary power source has been rendered substantially non-removable by a consumer to prevent a consumer from disabling the missing power source indicator by removing the supplementary power source. For example, in one embodiment of the present invention, the supplementary power source of the present invention is a battery which has been completely enclosed in plastic, thus being rendered substantially non-removable by a consumer in the absence of using physical force to alter the smoke detector circuitry or housing.