Central bank is the institution in charge of the public interests associated with the currency. It originates from fundamental changes in the technology of payments: the adoption of banknotes, cheques and giros, and their final disconnection from gold. These changes have shaped the two other functions that most central banks have derived from the original payment system function: monetary policy and banking supervision. Man-made money made monetary policy possible. Commercial bank money made banking supervision necessary.
Eurosystem is the word chosen by the ECB to indicate the "ECB+11 participating national central banks", i.e. the central bank of the euro. The Treaty has no name for this key entity, while it refers extensively to the ESCB (European System of Central Banks) formed by the ECB and the 15 European national central banks). However, as long as there are "out" countries, the ESCB in its full composition will remain a scarcely relevant entity because it neither refers to a single currency area nor has any policy competence. Instead, the word Eurosystem indicates clearly the articulated entity which is for the euro what the Federal Reserve System is for the dollar.
In legal and institutional terms, the result of this long fight has been engraved in the Treaty of Maastricht. The Treaty represents the strongest monetary constitution ever written, not only because of its substance, but also because the procedure to amend it is more difficult than that required for the charter of any existing central bank. Largely induced by Maastricht and EMU is also the independent status of national central banks in the European Union. We should indeed not forget that, until recently, key decisions in the field of monetary policy were still in the hands of the Treasury in such countries as the United Kingdom, France, Italy and Spain. The Maastricht process has been the catalyst for monetary reforms central bankers had advocated for years.
Different policies carry different degrees of compulsion and effectiveness. In general, instruments are more strongly framed when they are entrusted to institutions whose area of jurisdiction coincides with that of the nation state. Strongly framed instruments, however, do not necessarily produce strong results. Tough regulation against air pollution adopted only by a small country is less effective, for that same country, than softer regulation adopted by a larger group of countries. The economic literature about externalities, or that about optimal currency areas, are seminal examples of the contribution economic research can make in this respect.