What is the effect of being prone in the Ubiquity RPG system?

In the Ubiquity RPG system (used for Hollow Earth Expedition and other games), the action “Stand Up” reads : “Falling down is easy; it is getting up that is hard. Your character can fall prone as a reflexive action, but standing up requires him to give up an attack action. Your character can move and defend normally after getting to his feet.”

However, I cannot seem to find anywhere what the defence and movement implications of being prone are.

What are the effects on movement and defence (and other effects) of being prone in the Ubiquity system?