| 摘要 |
<p>A call point comprising a frangible element 9 which is mounted within a housing 1 and exposed via a window 8 to enable it to be broken or displaced to indicate an alarm situation. The breakage or displacement of the frangible element causes a cam/lever assembly to rotate about an axis 10 moving a magnet carried on a lever 12 away from a reed switch 15, thus causing the reed switch contacts to change state. The reed switch is mounted in a sealed chamber 6 so that sparking at its contacts cannot ignite the ambient atmosphere, and operates by virtue of the magnetic influence of the magnet through the wall 17 of the chamber 6.</p> |
