Currency board Helena continue to operate currency boards, backing their locally printed currency notes with pound sterling reserves. A gold standard is a special case of a currency board where the value of the national currency is linked to the value of gold instead of a foreign currency. For a precise definition of what constitutes a currency board, including past examples, see: Currency board A currency board is a monetary authority which is required to maintain a fixed exchange rate with a foreign currency. This policy objective requires the conventional objectives of a central bank to be subordinated to the exchange rate
S-train expansion and new trains). Plans for further extension of system include another two lines, one of which should reach Belgrade Nikola Tesla Airport. "S-Bahn" is also used in German-speaking Switzerland. While French publications of those networks translate it as "RER", the line numbers are still prefixed with an S (e.g. S2). The oldest network in Switzerland is the Bern S-Bahn, established in stages from 1974 and has adopted the term S-Bahn since 1995. It is also the only one in Switzerland to use a coloured "S" logo. In 1990, the Zürich S-Bahn, which covers the largest area, went into service.