The Sony Walkman portable cassette player was introduced in Japan in 1979 as the TPS-L2, a stereo follow-up to the monaural Sony Pressman. The blue-and-silver device ran on a pair of AA batteries and unlike portable radios of the day, it dispensed with speakers entirely in favor of headphones. In fact, the original Walkman had two headphone jacks. By the summer of 1980, Walkmans were on the shelves of retailers in the United States, and by 1983 cassette tapes were outselling vinyl records for the first time. For two decades, the Walkman and its compact-disc cousin, the Discman, dominated the portable-music-device market, but the party came to an end in 2001 when Apple introduced the iPod.