Gain is required because the signal intercepted by an antenna will have a very low power level, on the order of picowatts or femtowatts. To produce an audible signal in a pair of headphones requires this signal to be amplified a trillion-fold or more. The magnitudes of the required gain are so great that the logarithmic unit decibel is preferred - a gain of 1 trillion times the power is 120 decibels, which is a value achieved by many common receivers. Gain is provided by one or more amplifier stages in a receiver design; some of the gain is applied at the radio-frequency part of the system, and the rest at the frequencies used by the recovered information (audio, video, or data signals).