Actually more than that:

A Ram Air Turbine (RAT) serves as an emergency source of electrical and
hydraulic power. It has no operating time limits, airspeeds, or altitudes.
In flight, the RAT deploys automatically if any of the following occur:
• both engines have failed
• all three hydraulic system pressures are low
• loss of all electrical power to captain’s and first officer’s flight
instruments
• loss of all four EMPs and faults in the flight control system occur on
approach
• loss of all four EMPs and an engine fails on takeoff or landing
The RAT can be deployed manually if necessary by pushing the RAM AIR
TURBINE switch on the hydraulic panel.


On the B777 it is this by comparison:

In flight, the RAT
deploys automatically if:
• both engines are failed and center system pressure is low, or
• both AC transfer busses are unpowered, or
• all three hydraulic system pressures are low
The RAT can be deployed manually by pushing the RAM AIR TURBINE switch.
The hot battery or APU battery bus must be powered. The center hydraulic system
does not need to be powered. The RAT is deployed by a compressed spring. Once
deployed, the RAT cannot be stowed in flight.