The bump and go trolleys are designed with a switch in either end that is activated when the end bumper on the trolley contacts the stop/end-of-line barricade. These mechanical switches were not designed for all day train show use, IMO. The Dallee electronics takes advantage of a better trolley that uses Forward/Neutral/Reverse electronic reversing.
Here is a link to the Dallee instructions and wiring diagram. Click on the underlined phrase.
