| 摘要 |
<p>The detection is installed between the two panes of a double glazed window frame. An electronic control unit at the top of the frame causes a transmitting diode to emit a beam of IR light towards the bottom of the hermetically sealed volume enclosed by the glass. The beam, which is at a slight angle to the vertical, is reflected back to the top of the frame by a mirror. It is then repeatedly reflected between this mirror and another at the top until it is received and detected by a light-sensitive diode at the other side of the frame. Anyone breaking the window, and trying to enter will break the beam raising an alarm.</p> |
