An electric gas strut, also called an electric linear actuator, can be used to lift and close the service window of a food trailer. The system is simple: AC power enters a power supply/transformer, the transformer outputs DC power, and a forward-reverse switch changes the DC polarity to make the strut extend or retract.
The supplied wiring drawing shows five terminals on the transformer side: L, N, ground, V+ and V-. The DC output V+ and V- are connected to a forward-reverse switch, and the switch output is connected to the electric strut terminals V+ and V-.