Currency band

The currency band is a system of exchange rates by which a floating currency is backed by hard money.

A country selects a range, or "band", of values at which to set their currency, and returns to a fixed exchange rate if the value of their currency shifts outside this band.

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 This allows for some revaluation, but tends to stabilize the currency's value within the band. In this sense, it is a compromise between a fixed (or "pegged") exchange rate and a floating exchange rate. For example, the exchange rate of the renminbi of the mainland of the People's Republic of China has recently been based upon a currency band; the European Economic Community's "snake in the tunnel" was a similar concept that failed, but ultimately led to the establishment of the European Exchange Rate Mechanism (ERM) and ultimately the Euro.

(source:wikipedia)