The “Trig.” switch is used to configure the trigger coupling.
In position “AC” (alternating current coupling) the trigger signal is RC-coupled. Its direct current component is filtered. This means that signals, which have a frequency lower than the lowest frequency the oscilloscope allows, cannot be triggered. In this simulation however there is no low frequency limit. In position “DC” (direct current coupling) all signal components starting at 0 Hz influence triggering.
In position “”HF” (for “high frequency”), low frequent signal components are filtered, in position “LF” (for “low frequency”) high frequent signal components are filtered. These positions are used to filter noise. Noise amplitudes can trigger unwanted sweeps.
In position “~” the signal is triggered by the power supply frequency (in Germany i.e. 50 Hz, in the U.S. 60 Hz).
The Simulation does not support realtime triggering, because the calculation power needed for it cannot be achieved using the Macromedia scripting language “Lingo” in combination with current processors. Therefor the oscilloscope always behaves as if the “Trig.” switch was set to “AC”. The switch can be moved, but settings different from “AC” do not influence the signal processing.