The so called station-to-archive format which BSRN uses cannot be understood without reading the BSRN format manual (or see here for a more recent summary). The BSRN-Toolbox was developed to convert the station-to-archive format to more readable dataset tables to be able to plot and check the data. A documentation of the ToolBox ist available at:

You can download the BSRN-ToolBox here.