| 摘要 |
<p>An infra-red movement detector in a ball-joint on a mounting plate is installed in a standard mains switch box sunk in a wall flush with the plaster. It is secured by clips, levered outwards by tightening screws. It is covered by an escutcheon plate with a hole covered by a grid backed by poly-ethylene foil. This thus provides a cheap, inconspicuous installation of a burglar alarm, suitable for any room and easily installed with concealed wiring.</p> |
