Reel-to-reel tape was used in early tape drives for data storage on mainframe computers and in video tape recorders (VTRs). Magnetic tape was also used to record data signals for instrumentation purposes, beginning with the hydrogen bomb tests of the early 1950s. Studer, Stellavox, Tascam, and Denon still produced reel to reel tape recorders in the 1990s, but , only Mechlabor continues to manufacture analog reel-to-reel recorders. Currently (2020), there are two companies that manufacture magnetic recording tape: ATR Services of York, Pennsylvania, and Recording the Masters in Avranches, France.