To bring back higher frequencies to their original level - This accurately describes the function of the de-emphasis circuit. Circuit Location Function Effect on High Frequencies (HF) Pre-emphasis Transmitter Boosts HF to improve S/N ratio during transmission Boosts HF level De-emphasis Receiver Attenuates boosted HF to restore original frequency response Reduces (attenuates) HF level Therefore, the main function of a de-emphasis circuit is to compensate for the pre-emphasis applied at the transmitter, specifically by bringing the higher frequencies back to their original relative levels.