Extended Data Services

Extended Data Services (now XDS, previously EDS), is an American standard classified under Electronic Industries Alliance standard EIA-766 for the delivery of any ancillary data (metadata) to be sent with an analog television program, or any other NTSC video signal.

XDS is used by TV stations, TV networks, and TV program syndication distributors in the USA for several purposes.

Here are some of the most common uses of XDS:

The "autoclock" system delivers time data via an XDS "Time-of-Day Packet" for automatically setting the clock of newer TVs & VCRs sold in the USA. Most PBS stations provide this service.
Rudimentary program information which can be displayed on-screen, such as the name and remaining time of the program,
Station identification,
V-chip content ratings data.

XDS is also used by the American TV network ABC for their Network Alert System (NAS). NAS is a one-way communication system used by ABC to inform and alert their local affiliate stations across the USA of information regarding ABC's network programming (such as program timings & changes, news special report information, etc.), using a special decoder manufactured for ABC by EEG Enterprises [1], a manufacturer of related equipment for the TV broadcast industry such as closed captioning and general-purpose XDS encoders.

XDS uses the same line in the VBI as closed captioning (NTSC line 21), but it utilizes the second video field (as opposed to closed captioning's line 21, field 1).