Lex.bin is the first phase of the compiler. It takes a .spn file as input, tokenizes it, and writes the result to a .tok file. On successful completion, lex.bin can automatically run codegen.bin, the next compiler phase.
lex filename [options]
lex tv_text /c
This command tokenizes tv_text.spn, producing tv_text.tok, and then runs codegen.bin. Note that you don't have to add ".spn" to the input filename. Lex.bin will add it automatically.
You should never have to run lex.bin directly; instead, use the convenient c command (provided by sphinx.bin) which is equivalent to running lex with the /c option.