A radar advisory service (RAS), is a radar service provided to pilots flying IFR outside controlled airspace. Details on direction, level (if known) of any conflicting traffic (which may not be working the same unit or any unit at all) will be passed along with any ADVICE for avoidance. Vectors are provided and pilots are expected to comply with any avoiding action. Should a pilot refuse to comply with these instructions, then they become responsible for their own separation from the conflicting traffic.
RAS is only avaible to IFR traffic outside controlled airspace.
RCS (radar control servoce) is only available INSIDE controlled airspace