SCA - Subsidiary Communications Authority

Subsidiary Communications Authority or SCA, is a term used by the U.S. based FCC to denote a separate audio or data channel which is transmitted along with the main audio signal over a broadcast station. This channel is transmitted over a so-called subcarrier. These subcarrier channels are not receivable with a regular radio. A special receiver is required to receive the information.

Subcarriers are used for many different purposes, including (but not limited to) paging, inventory distribution, bus dispatching, stock market reports, traffic control signal switching, point-to-point or multipoint messages, foreign language programming, radio reading services, radio broadcast data systems (RBDS), station control and meter reading, utility load management, and muzak. A broadcast station may transmit more than one subcarrier signal.