Communication Systems
In case of frequency modulation, modulating voltage remains constant if the modulating frequency is lowered, then

Amplitude of distant sidebands remains constant
Amplitude of distant sidebands first increases, then decreases
Amplitude of distant sidebands decreases
Amplitude of distant sidebands increases

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Communication Systems
In Pulse Code Modulation system

Quantising noise can be overcome by companding
Suffers from the disadvantage of its incompatibly with TDM
Quantising noise can be reduced by decreasing the number of standard levels
Large bandwidth is required

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