A central bank affects the monetary base through open market operations, if its country has a well developed market for its government bonds. This entails managing the quantity of money in circulation through the buying and selling of various financial instruments, such as treasury bills, repurchase agreements or "repos", company bonds, or foreign currencies, in exchange for money on deposit at the central bank. Those deposits are convertible to currency, so all of these purchases or sales result in more or less base currency entering or leaving market circulation.
A central bank affects the monetary base through open market operations if its country has a well developed market for its government bonds. This entails managing the quantity of money in circulation through the buying and selling of various financial instruments, such as treasury bills, repurchase agreements or "repos", company bonds, or foreign currencies, in exchange for money on deposit at the central bank. Those deposits are convertible to currency, so all of these purchases or sales result in more or less base currency entering or leaving market circulation.