The signal is then fed into a circuit where it is mixed with a sine wave from a variable frequency oscillator known as the local oscillator (LO). The mixer uses a non-linear component to produce both sum and difference beat frequencies signals, each one containing the modulation contained in the desired signal. The output of the mixer may include the original RF signal at "f"RF, the local oscillator signal at "f"LO, and the two new heterodyne frequencies "f"RF + "f"LO and "f"RF − "f"LO. The mixer may inadvertently produce additional frequencies such as third- and higher-order intermodulation products. Ideally, the IF bandpass filter removes all but the desired IF signal at "f"IF. The IF signal contains the original modulation (transmitted information) that the received radio signal had at "f"RF.