Spectrum version 3.2 was released in 2009 as an update to Spectrum v.3.0. By clicking on the download link on this page, you can access Spectrum 3.2 as a pdf. The document includes the standard and the units of information. This version has now been archived and so many of the links within the text will no longer work.
The latest version of the Spectrum standard was launched in September 2017 and is available at the link below: