The discount window is an instrument of monetary policy (usually controlled by central banks) that allows eligible institutions to borrow money from the central bank, usually on a short-term basis, to meet temporary shortages of liquidity caused by internal or external disruptions. The term originated with the practice of sending a bank representative to a reserve bank teller window when a bank needed to borrow money. The interest rate charged on such loans by a central bank is called the discount rate, policy rate, base rate, or repo rate, and is separate and distinct from the prime rate. It is also not the same thing as the federal funds rate or its equivalents in other currencies, which determine the rate at which banks lend money to each other. In recent years, the discount rate has been approximately a percentage point above the federal funds rate (see Lombard credit). Because of this, it is a relatively unimportant factor in the control of the money supply and is only taken advantage of at large volume during emergencies. In the United States In the United States, there are actually several different rates charged to institutions borrowing at the Discount Window. In 2006, these were: the primary credit rate (the most common), the secondary credit rate (for banks that are less financially sound), and the seasonal credit rate. The Federal Reserve does not publish information regarding institutions' eligibility for primary or secondary credit. Primary and secondary credit is normally offered on a secured overnight basis, while seasonal credit is extended up to nine months. The primary credit is normally set 100 basis points (bp) above the federal funds target and the secondary credit rate is set 50 bp above the primary rate. The seasonal credit rate is set from an averaging of the effective federal funds rate and 90-day certificate of deposit rates. Institutions must provide acceptable collateral to secure the loan. Use after September 11, 2001 After the 11 September 2001 attacks, as the volume of borrowing requests increased dramatically, lending to banks through the discount window totaled about $46 billion, more than 200 times the daily average for the previous month. The flood of funds released into the banking system reduced the immediate need for banks to rely on payments from other banks so they could pay what they owed others. That kept liquidity alive in the economy despite interruptions of communications