What does XM stand for? 

XM

XM Satellite Radio (XM) was one of the three satellite radio (SDARS) and online radio services in the United States and Canada, operated by Sirius XM Holdings. It provided pay-for-service radio, analogous to subscription cable television. Its service included 73 different music channels, 39 news, sports, talk and entertainment channels, 21 regional traffic and weather channels, and 23 play-by-play sports channels. XM channels were identified by Arbitron with the label "XM" (e.g., "XM32" for "The Bridge"). The company had its origins in the 1988 formation of the American Mobile Satellite Corporation (AMSC), a consortium of several organizations originally dedicated to satellite broadcasting of telephone, fax, and data signals. In 1992, AMSC established a unit called the American Mobile Radio Corporation dedicated to developing a satellite-based digital radio service; this was spun off as XM Satellite Radio Holdings, Inc. in 1999. The satellite service officially launched on September 25, 2001. On July 29, 2008, XM and former competitor Sirius Satellite Radio formally completed their merger, following U.S. Federal Communications Commission (FCC) approval, forming Sirius XM Radio, Inc. with XM Satellite Radio, Inc. as its subsidiary. On November 12, 2008, Sirius and XM began broadcasting with their new, combined channel lineups. On January 13, 2011, XM Satellite Radio, Inc. was dissolved as a separate entity and merged into Sirius XM Radio, Inc.

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