Since 9 January 1984, all the West Berlin S-Bahn routes are labelled with an "S" followed by a number. This system had been in use with other West German S-Bahn systems (such as Hamburg) for years. On 2 June 1991 this was extended to the East Berlin lines as well. Internally, the Berlin S-Bahn uses "Zuggruppen" (literally groups of trains) which normally run every twenty minutes (S41/S42 are an exception to this as their Zuggruppen run every 10 minutes). Some lines, e.g. the S85, are made up of only one Zuggruppe, while others, like S5, are actually multiple Zuggruppen combined. Some Zuggruppen do not run the entire line and terminate at intermediate stops. Zuggruppen are called by a "Funkname" (radio designator), which is derived from the German spelling alphabet. Some Funknamen are not used in regular service, such as Heinrich, Baikal, Jaguar, Gustav, or Saale (being used for special soccer service trains, usually running for fans under the line S3 between Charlottenburg and Olympiastadion.).