| CPC A62C 37/50 (2013.01) [A62C 37/11 (2013.01); G01L 9/0005 (2013.01)] | 15 Claims |

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1. A sprinkler bulb comprising a sealed frangible housing (110), and a circuit device (120) sealed within the housing and without external wired connections, wherein the circuit device comprises:
a capacitor (150) within the housing (110) arranged to be used as a pressure sensor to detect pressure changes within the housing (110);
a heating element operable to heat fluid within the housing of the sprinkler bulb, and
a control unit configured to monitor changes in the capacitance of the capacitor and thereby use the capacitor as a pressure sensor.
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