摘要 |
An alarm unit is provided for attachment to a wall surface. The alarm unit includes a back plate and a plastic outer cover. The cover is attached to the back plate by a hinge. The hinge has an orientation such that when the alarm unit is attached to a wall surface, hinged movement of the cover away from the back plate is assisted by gravity. The cover may be retained in position against the back plate by one or more screws which may be provided with a sliding cover. |