Abstract: A portable light for emergency illumination which is activated in response to the sound emitted by a smoke alarm device, which light has an efficient and reliable battery conserving circuit. The present light includes a switch interconnecting a battery and a light bulb for selectively activating the light bulb and a circuit interconnecting a microphone and the switch for selectively activating the switch in response to a smoke alarm signal. A strobe circuit interconnects the source of power and the circuit for periodically activating the circuit which, therefore, draws power for only a small fraction of the time.

Abstract: A portable light for emergency illumination which is activated in response to the sound emitted by a smoke alarm device. The circuit is highly simplified, making it producible in quantity, and has a performance which is highly predictable. The circuit has a very low battery drain so that it will operate from a small battery for a period of years. The circuit is highly insensitive to extraneous noise signals and utilizes the normal drop in battery voltage when the light comes on to prevent the circuit from going into an oscillation mode.