in America, supplying record manufacturers like Philco, RCA, Emerson, Magnavox, Admiral, and Motorola. At the peak of Shure's production the company was producing more than 28,000 cartridges per day, with 25,000 produced at Shure's Phoenix plant. While Shure continues to manufacture phono cartridges, the Phoenix facility was closed in the late 1980s due to declining demand. Shure engineers introduced several key phono cartridge design concepts. Chief engineer Ralph Glover discussed the pickup design relationship to record wear in a 1937 article in Electronics magazine entitled "A Record-Saving Pickup". Glover developed the "needle-tilt" principle with the assistance of fellow Shure engineer Ben Bauer, and considerations of needle angle, record wear, and fidelity were an integral part of Shure's cartridge designs. In 1966, chief engineer Jim Kogen published a research paper entitled "TRACKability" in Audio magazine, defining the concept as the ability of a cartridge to maintain contact with a record groove through any modulation. Shure is credited with several industry firsts. In 1948, the company introduced the 900MG, the first phonograph cartridge capable of playing both long-playing and 78 rpm records, and in 1954, Shure's M12 Dynetic Phono Reproducer tonearm and cartridge set established an industry standard with a tracking force of only one gram. The M1 Studio Dynetic Cartridge introduced the principle of a moving magnet within a stationary coil, an engineering concept that dominated cartridge design for nearly 25 years due to its higher output, lower noise, and greater headroom. The Shure M3D, introduced in 1958, was the first ever stereo moving magnet cartridge, with 20 dB of stereo separation at 20 kHz. Shure has also designed and manufactured cartridges specifically for disc jockeys. Their M35X and Whitelabel cartridges are designed for nightclubs. The M44-7, however, is designed for scratching, which involves playing a vinyl record forward and backward rhythmically. The M44-7 cartridge is renowned for its tracking and skip resistance, which has made it a popular choice of turntablists such as The Invisibl Skratch Piklz. Shure's flagship V15 phonograph cartridge series, with the model name referring to their 15-degree tracking angle, was established for decades as the premier cartridge for low tracking force and high tracking ability. The V-15 series also included several industry firsts: the original V-15 model (introduced in 1964) was the first to feature "trackability", and utilized a symmetrical, bi-radial elliptical stylus. The V-15 Type II (introduced in 1966) was the first computer-designed phono cartridge