what is function of capacitor

[ewerebellatok]

waht is funtion of capacitor in this circuit??
what happen to the circuit if that capacitor is cancel out??
http://www.electronic-circuits-diagrams.com/alarmsimages/alarmsckt19.shtml

 

[prateeksikka]

i cant see the diagram very  clearly but still i can say that some times the capacitors have to be used for supply filtering too i.e to remove the ripples in a dc supply.the purpose may not look  very promising to a newbie!!!