National Datacast Incorporated (NDI) was a pioneer in data broadcasting. It was a for-profit subsidiary of the Public Broadcasting Service (PBS) which it the subsidy's final years had a minority stake. it handled datacasting on PBS TV stations throughout the United States. Services using ATSC digital TV include MovieBeam and UpdateTV, for which bandwidth is leased by other companies.
It used line 21 and other vertical interval lines for data transmission.
It ceased operations in 2015.