On the green system the normal source of pressure is the Engine DrivenPump (EDP) and as auxiliary source the Power Transfer Unit (PTU).On the blue system the normal source of pressure is the electrical pump(E-Pump) and as auxiliary source the Ram Air Turbine (RAT).NOTE: The blue electric pump can be used as an auxiliary power sourcefor maintenance purposes on ground.On the yellow system the normal source of pressure is the EDP and asauxiliary sources the PTU and the electric pump (E- Pump).NOTE: The yellow system also has a hand pump dedicated to cargodoor operation.