A control user interface includes a first control for selecting a value for an output parameter of an electronic device, a second control for switching between different modes of a first function, and a third control for turning the device off. In response to an input directed to the control user interface: if the input is directed to the first control, the device adjusts a current value for the output parameter; if the input is directed to the second control and meets first criteria, the device changes a current mode of the first function; if the input is directed to the third control and meets second input criteria, the device initiates a process for turning off the device; and if the input is directed to the third control and meets the first criteria but not the second criteria, the device forgoes initiation of the process for turning off the device.