The orange FUNCTION button corresponds to the orange marking around the dial. AC millivolts, continuity, diode testing, AC microAmps, and AC milliAmps are controlled with the FUNCTION button. As with the other button functions, just press the FUNCTION button and it will toggle through the dial functions. Once the desired function is reached, the meter is ready to read the incoming signal. Press and hold it for approximately three seconds and it deactivates.