| 摘要 |
A light source arranged to be illuminated automatically upon failure of the normal electricity supply to a room, building or the like. The light source comprises a lamp housing containing a bulb, batteries and switch, and a base on which the lamp housing can be mounted. One part of an electromagnet including an energizing winding is mounted in the base and the other part is mounted in the torch housing such that when the housing is mounted on the base and an a.c. supply is made to the base, the two parts of the electromagnet are mutually attracted and the housing is held securely on the base. If the a.c. supply is interrupted the electromagnet is de-energized, allowing the housing to be removed from the base and, at the same time, the switch is operated to connect the batteries to supply current to the bulb.
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