 An oscilloscope's trigger setting specifies a synchronization or anchor point to use for drawing a signal's waveform on the display. If the trigger is too high, the wave will roll chaotically, but lowering the trigger value till it's within the signal's voltage range will bring peace to a periodic waveform, making it much easier to measure. There are several common trigger modes to choose from. Edge mode, the default, triggers the display when the signal reaches a specified voltage level on either the rising or falling edge of the waveform. Pulse mode triggers display on detection of a pulse with a specific width. Slope mode triggers on an incline or decline in the signal of a specific width. Video trigger mode allows you to sync to a specific section of a standard NTSC or PAL video signal. You can even jump to a specific line number of the video image.