Used when operations entities are documented in the Common Reference Database, or in the Retail Reference Database. According to the RNE CRD documentation (https://ccs.rne.eu/crd/ ), "Locations can be stations, yards, halts, terminal or transshipment points, loading points, marker points, warehouses, maintenance workshops, traction departments, town offices, railway frontier-points, transit-points, hand-over points, interchange points and customer sidings." Historical note: Primary and secondary code are historically related to French CI / CH (code immuable / code chantier) taxonomy. Primary codes were listed in UIC 920-1, encompassing all sorts of locations used in international data exchange, including town offices. In practice, TAF/TAP mostly handles on-network locations. Town office codes are stored in RRD (retail reference database), not CRD. The same place may have to codes, one in CRD, one in RRD, according to usage. Primary code is 7-digit string, starting with 2-letter ISO country code. RRD uses 2-digit UIC country code instead (e.g. 80 for Germany). Secondary code starts with 2 digits ("subsidiary type").