approximately one year beginning in November 2008, after which WNYZ-LD reverted to low-power analog. The assignment of virtual channels in the United States is defined within the stream via terrestrial or cable versions of a "Virtual Channel Table" as outlined by ATSC document "A/65", Annex B. Rules for assignment of major channel numbers are as follows: Existing analog stations were assigned a major channel number matching their existing analog number New digital stations assigned to a channel whose matching major channel number is not in use must use that number New digital stations assigned to a channel whose matching major channel number is in use (by a former analog station) must reciprocate, using the major channel number that matches the actual channel of the station in question. These rules generally ensure that no overlapping will occur, although in the case of stations where large numbers of stations in adjacent markets are in close proximity to each other, it is possible that such overlap can occasionally happen (see, for example, the case of WJLP). Additionally, stations may broadcast some of their subchannels under major channel(s) in the 70–99 range, so long as multiple stations do not attempt to use the same major channel(s). These numbers are certain to be unused, as 69 was the highest assigned channel prior to the conversion to digital broadcasting. The document does not address the use of certain other major channel numbers: Numbers below 70 that were never used in NTSC (0, 1 and 37) The real numbers of stations that are using virtual channels from 38 to 69 (these stations are not covered by the reciprocity rule, as real station numbers are not assigned above 36) Numbers in the range of 38–69 that are not being used by a former analog station Additionally, broadcasters owning more than one station that overlap in coverage area may set all of the channels to use the major channel of just one of the stations, so long as different minor channel numbers are used to avoid overlap. When the United States began buying back licenses in a broadcast spectrum auction in 2017, it also allowed companies that had a duopoly in a market to sell one of the licenses but continue to use the virtual channel of the sold channel on a subchannel of the other. For example, Sunbeam Television sold WLVI in the auction, but in turn was