The button labelled “Ch I/II” (and “Trig I/II”) is a channel selector button. “Ch” stands for “Channel”. In single channel operating mode the button determines, which one of the input signals is displayed on the screen. If the button is off, the signal in channel 1 will be displayed, if it is on, the signal in channel 2 will be shown.
In dual operating mode (“Dual”, “Chop” or “Add” mode) the setting of the button determines which of the signals delivers the data for calculating the trigger timing. In this simulation however it is impossible to get realtime-triggering for cpu timing limitations. Instead, both channels are triggered at the same time.