Active equipment that receives the signal (microwave) reflected by the satellite dish and converts it into radio frequency to be transmitted by the distribution system. The frequency to which the satellite signal is shifted is known as intermediate frequency (IF).
The LNB includes an amplifier with a very low noise figure (hence the name Low Noise Block), a bandpass filter that limits the noise entering the next equipment, a combiner, and a local oscillator to switch bands (18 V + 22 kHz = HH; 18 V = HL; 13 V + 22 kHz = VH; 13 V = VL); finally, there is a block for IF amplification prior to transmission.