The amplitude of the signal may be scaled, i.e. increased (amplification) or reduced (attenuation). A scaling system may be modelled in terms of multiplication of the amplitude of the signal by a scaling value s:
In the context of a sinusoid signal, this can be represented as follows:
If s > 1, then the signal is amplified; if 
, then the signal is attenuated; if s=1 then the signal amplitude remains unaffected.
A simple operational model for the amplification operation is the amplifier of a radio, cassette recorder, hifi system, etc. The volume control is used for a simple kind of amplitude modulation of the signal by varying the amount of amplification.