In American and Canadian metropolitan areas, XM and its Canadian licensee "Canadian Satellite Radio" (CSR) and operating as Sirius XM Canada, owned and operated a network of approximately 900 terrestrial repeater stations, meant to compensate for satellite signal blockage by buildings, tunnels, and bridges. In the United States, XM owned and operated approximately 800 repeater sites, covering 60 markets; in Canada, CSR was installing approximately 80 to 100 repeaters that were planned to be owned and operated by CSR in the 16 largest Canadian cities. The actual number of repeater sites varies as the signal is regularly tested and monitored for optimal performance. The actual number of sites in the United States has dropped from the original 1,000 installed when the service first launched in 2001. The repeaters transmit in the same frequency band as the satellites. A typical city contains 20 or more terrestrial stations. Typically, the receiver owner is unaware when a terrestrial station is being used, unless he or she checks antenna information from the receiver being used. Due to a FCC filing in October 2006, the latest list of XM's US terrestrial repeater network was made available to the public.