The amplifier is a device allowing you to monitor the antenna gain, expressed in dB, by adjusting intensity of the signal input or output. Generally the amplifier allows the adjustment of the signal power in order to optimize the reception: it amplifies the weaker signals or dramps the stronger ones.The amplifier is provided with A/B switch function which, if an alternative TV connection is available (for instance from dock), allows cut off the TV-signal reception of your antenna and to receive directly from another source.Technical Specification-- INPUT 2 inputs, one from the antenna and one from the dock (A/B switch) -- OUTPUT 1 output to TV or 2/4 way splitter (max 4) -- AMPLIFIER BY-PASS No -- POWER SUPPLY 12Vdc-- ADJUSTABLE GAIN AVERAGE max 27,5 dB-- NOISE FACTOR 2,1 dB -- A/B SWITCH When the knob is turned to the "A" input antenna, the amplifier is on. When it's turned on "B" it means that the input is from the dock of from another source, and that the amplifier is off.