Preemphasis network

In telecommunication, a preemphasis network is a network inserted in a system in order to increase the magnitude of one range of frequencies with respect to another.

Note: Preemphasis is usually employed in FM or phase modulation transmitters to equalize the modulating signal drive power in terms of deviation ratio. The receiver demodulation process includes a reciprocal network, called a deemphasis network, to restore the original signal power distribution.

Source: from Federal Standard 1037C and from MIL-STD-188