... You are here: start €Ё difx €Ё difx2mark4 €Ё stationcodes . ... difx:difx2mark4:stationcodes . The Mark4 correlation system represents stations with a single letter. ... There is a default mapping (compiled in) which includes a number of stations and seven empty slots to be used as stations not in the table are encountered: . ... As each station not in the table is found, an xx entry in the table above is assigned to that station and the corresponding single letter code is used thereafter. ...