Dolby SR (SR is the abbreviation for Spectral Recording) was introduced in 1986 as Dolby’s second generation professional recording system. Not only was it designed to provide more noise reduction than past systems, but it also provided a number of other technological innovations that extend the recording’s dynamic range and allowed a very high quality master recording (very nearly digital). Thus SR is referred to as a signal processing system rather than just a noise reduction system. SR arrived on the scene not long after some of the first high-end digital machines appeared and it was instrumental in keeping analog recording viable at a time when everyone wanted the noiseless (if antiseptic) sound of digital recording. Just about every serious studio with a 2″ 24-track had an SR rack next to it. SR never found its way into consumer recording machines due to the extreme cost of the electronics and due to sensitive calibration issues.