Definição do conceito
[ENG] 45 rpm | Phonograph records are generally described by their diameter in inches (12-inch, 10-inch, 7-inch) (although they were designed in millimeters), the rotational speed in revolutions per minute (rpm) at which they are played (8+1?3, 16+2?3, 33+1?3, 45, 78),[8] and their time capacity, determined by their diameter and speed (LP [long playing], 12-inch disc, 33+1?3 rpm; SP [single], 10-inch disc, 78 rpm, or 7-inch disc, 45 rpm; EP [extended play], 12-inch disc or 7-inch disc, 33+1?3 or 45 rpm); their reproductive quality, or level of fidelity (high-fidelity, orthophonic, full-range, etc.); and the number of audio channels (mono, stereo, quad, etc.). || .../... in February 1949, RCA Victor released the first 45 rpm single, 7 inches in diameter with a large center hole. The 45 rpm player included a changing mechanism that allowed multiple disks to be stacked, much as a conventional changer handled 78s. The short playing time of a single 45 rpm side meant that long works, such as symphonies, had to be released on multiple 45s instead of a single LP, but RCA Victor claimed that the new high-speed changer rendered side breaks so brief as to be inaudible or inconsequential. Early 45 rpm records were made from either vinyl or polystyrene. They had a playing time of eight minutes. || .../... The 45 rpm discs also came in a variety known as extended play (EP), which achieved up to 10–15 minutes play at the expense of attenuating (and possibly compressing) the sound to reduce the width required by the groove. EP discs were cheaper to produce and were used in cases where unit sales were likely to be more limited or to reissue LP albums on the smaller format for those people who had only 45 rpm players. || SOURCE : Phonograph record. in: Wikipedia. Available at : https://en.wikipedia.org/wiki/Phonograph_record Accessed : 20 sep. 2022
=====================================
