View source for Automatic Transmitter Identification System (television)

{{Short description|Satellite TV station identification protocol}}
{{about|the satellite TV protocol|the maritime vessel system|Automatic Transmitter Identification System (marine)|the airport weather transmitting system|Automatic terminal information service}}
{{moreref|date=July 2008}}

The '''Automatic Transmitter Identification System''' ('''ATIS''') is a [[communications protocol]] used for the [[station identification]] of [[television channel]]s carried on [[satellite television]].<ref>{{cite journal|author1=K.G. Johannsen|title=Automatic transmitter identification system|journal=IEEE Transactions on Broadcasting|date=1992|volume=38|issue=2 |page=127-132|issn=0018-9316|doi=10.1109/11.142664}}</ref>

ATIS is only required for [[analog television]] transmission and only via satellites or [[earth station]]s under [[United States]] jurisdiction. It is continuously repeated whilst an earth station is using a [[transponder]] on a satellite. The [[Federal Communications Commission]] (FCC) rules for ATIS are set forth in [[CFR Title 47|47]] [[Code of Federal Regulations|CFR]] §25.281.

The system was developed in response to the "[[Captain Midnight broadcast signal intrusion|Captain Midnight]]" satellite jamming incident. In 2009, HBO and Elmer Musser were awarded a [[Technology & Engineering Emmy Award#2009 Awards|Technology & Engineering Emmy Award]] for ATIS.

ATIS is a [[Morse code]] transmission sent on a [[subcarrier]] of 7.1&nbsp;MHz and must activate automatically any time the station is transmitting. The [[center frequency]] must be no more than 25&nbsp;kHz from this [[nominal value]] and the [[frequency deviation]] must be no more than 25&nbsp;kHz peak when being [[modulation|modulated]]. Injection must be at a minimum of −26[[decibel|dB]] referenced to the [[unmodulated carrier]]. The [[pure tone|tone]] used to modulate the subcarrier is nominally 1200&nbsp;Hz, but may vary by as much as 800&nbsp;Hz (400 to 2000&nbsp;Hz).

The ATIS message is sent at a [[bit rate|transmission rate]] of 15 to 25 [[words per minute]] and must not exceed 30 seconds in its entire length. The message includes the FCC-assigned [[callsign]] of the earth station, its [[telephone number]], a ten-digit [[serial number]], and sometimes other information which is voluntary. The telephone number must immediately connect to personnel who can resolve [[radio interference]] and other [[frequency coordination]] issues. The serial number cannot be easily changed.

ATIS encoders must be included in the [[uplink]] [[airchain]] of all transmitters as of March 1, 1991 "in a method that cannot easily be defeated".

Other subcarriers piggybacked on the [[video]] carrier are also included in transmissions, often at 6.2&nbsp;MHz and 6.8&nbsp;MHz, just above the [[bandpass]] of the video signal (even if [[television encryption|scrambled]]). These carry left and right [[stereophonic sound|stereo]] audio and [[second audio program]], and sometimes [[radio station]]s or [[radio network]]s which may be unrelated to the [[television network]]. [[Backhaul (broadcasting)|Backhauls]] are too intermittent for such uses but may carry in-house private audio channels instead. Because all of these, including ATIS, are all audio, they can all be tuned by an analog [[Television receive-only|TVRO]] [[Receiver (radio)|receiver]]. However, [[digital television]] has overtaken analog because multiple channels can be transmitted on one transponder. These signals carry their station ID as [[data]] instead.

==References==
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[[Category:Satellite television]]
[[Category:Broadcast engineering]]