The 555 circuit shown above is more sophisticated than the circuit above and is composed of several components included the integrated circuit (NE555). When switched on the buzzer sounds for a certain amount of time. Some of the components are resistors and capacitors. It is often the combination of resistors and capacitors that control the time delay - in this case the length the buzzer sounds for. If the capacitor C1 is changed for a higher value capacitor then the buzzer sounds for a longer period of time. The variable resistor VR1 can also determine the length of time.