When the “Ext.” button is on (=”external”), the trigger timing of a real oscilloscope is not determined using the signal from channel 1 or 2 but from a signal attached to the external trigger input connector.

In this simulation however that is not the case because of cpu timing limitations for a realtime calculation of the trigger timing. The calculation cannot be done using the Macromedia scripting language “Lingo” and current processor speeds. It is possible to turn the button on and off and to attach a cable to the external trigger input connector, but the button setting and a signal attached do not influence trigger timing in this version of the simulation.