Abstract

A battery operated emergency lamp is provided for connection to a normally "on" electrical source of power, such as a standard ac line voltage, where such source is subject to occasional power failures. A solid state switching circuit including a single transistor and one diode serves to maintain the lamp in an unenergized condition and to simultaneously generate a low charging current for a re-chargeable battery so long as the power source remains "on." In the event of a power interruption, the solid state switching circuit is immediately responsive to switch to a condition in which the lamp is energized by the battery current. In one embodiment disclosed herein, the emergency lamp takes the form of a relatively small, portable lantern or flashlight equipped with a standard utility plug for connection to a household electrical outlet. With the lamp plugged into the wall receptacle, the light source is maintained in an unenergized state while the rechargeable battery is continously charged for availability in the event of an emergency blackout or other power loss. When the power failure does occur, the lamp is automatically turned "on" to provide emergency light and to indicate the position of the device for removal from the wall receptacle and use as a portable flashlight. Additionally, the light may be employed as a convenient, always ready, portable lantern in which its removal from the electrical receptacle automatically energizes the light.