A two-step pathway for preparing high pure quaternary phosphonium salts is disclosed. A computing device is configured to determine a Technetium-99m content of the eluate based on a first current measured in the inner ionization chamber, and determine a Molybdenum-99 content of the eluate based on at least a second current measured in the outer ionization chamber. The rail vehicle determines the light signal data assigned to the line block section by comparison of line block section specifics. The contact is then downloaded for storage and later use.