T-Mobile US Inc will pay $17.5 million to settle a U.S. investigation of two 911 service outages last year, marking the largest such fine by the Federal Communications Commission. The FCC on Friday said it found that better safeguards in T-Mobile’s 911 network architecture would have prevented the outages, which together lasted for about three hours on Aug. 8 and affected almost all of the wireless carriers’ 50 million customers nationwide. The FCC said it also found T-Mobile did not notify affected 911 call centers in a timely manner, as required by FCC rules.