Definition
An unstaffed VHF radio transceiver placed at a remote site that extends the communication range of a Flight Service Station (FSS). When a pilot transmits on the RCO frequency, the signal is relayed by landline or other link back to a controller or specialist at the parent FSS, who then responds through the same outlet.
Plain English
A small, unmanned radio antenna site in the field that lets pilots talk to a Flight Service specialist who is sitting somewhere far away. You speak to the box, the box passes your call to the person, and the person answers back through the same box.
Context Anchor
Seen on charts, in airport information, and in weather or flight-planning discussions when a pilot needs to contact Flight Service by radio.
Derivation
"Remote" because the outlet is located away from the staffed facility it serves, and "outlet" because it acts as an access point — a place where the pilot can plug into the FSS network by radio. Knowing this helps the pilot picture an RCO as a doorway to the FSS, not a facility that does anything on its own.
Why Pilots Care
It lets pilots in isolated areas obtain weather briefings, file flight plans, and receive advisories without needing to be within line-of-sight of a staffed facility.
Intuition Check
Do not assume the person you are talking to is physically at the RCO site. The radio equipment may be nearby, but it is controlled and answered from another location.
Example Sentence 1
Out of range of the FSS main antenna, the pilot called Flight Service through the RCO frequency printed on the sectional chart.
Example Sentence 2
While flying over sparsely populated terrain, the pilot used the RCO to open a VFR flight plan.