FieldWorks uses Unicode character encoding. The Unicode Standard is the universal character encoding scheme for written characters and text.
Select an encoding converter for a writing system only to import standard format files in which some of the imported text does not meet either of the following requirements:
It is encoded in Unicode (for example, in UTF-8, which is a variable length encoding of the Unicode Standard that uses 8-bit sequences).
Its encoding is compatible with the system language for non-Unicode programs.
Most FieldWorks users will require technical assistance with encoding converters.
If you need to add, copy, modify, or remove a converter, on the Converters tab of the Writing System Properties dialog box, click More.
The Encoding Converters dialog box appears.
Do any of the following:
To add, modify or remove a converter, click the Properties tab.
To convert sample text, click the Test tab.
To see the property values of a converter, click the Advanced tab.
Click Close.
Be aware that the selection in the Encoding converter for importing <language> (Converters tab) also changes if you select a different encoding converter in the Available Converters list.
Writing System Properties, Converters tab
https://software.sil.org/fieldworks/support/technical-documents/
https://scripts.sil.org/cms/scripts/page.php?cat_id=ConversionUtilities