The paper describes some properties of simple interconversion devices which enable material intially subject indexed by a particular indexing system to be made available to other institutions using different indexing languages in such a form as to be readily integrated into their indexes. Reference is made to the outline Intermediate Lexicon which is the germinal form of a switching language for the field of information science. Difficulties and problems in effecting satisfactory information transfer through such an interconversion scheme are explored, and suggestions made for the lines upon which further research needs to be undertaken. The author was the Classification Research Group representative on the international working party concerned with the Intermediate Lexicon.