Similarly, sales of securities from the Fed's financial portfolio result in debits against the accounts of commercial banks with the Fed and thus serve to drain reserve balances from the system.10 Collectively, these transactions are called open-market operations. Factors outside the control of the Open Market Desk can also affect the supply of reserve balances.
For example, when the Federal Reserve receives an order for currency from a bank, it debits the reserve account of the bank in payment when the currency is shipped, thereby reducing reserve supply. When deciding upon open market operations to control the supply of reserves, the Open Market Desk must take account of these external factors.