An AMPLIFIER is a device that increases the strength of an electrical signal, and can be used to increase the volume of sound waves. The term 'AMPLIFIER' can refer to a variety of devices, including a MASER (an acronym for Microwave Amplification by Stimulated Emission of Radiation), a TREBLE (an electronic device that boosts high-frequency sounds), a MIKE (a microphone), a MEGAPHONE (a cone-shaped device used to amplify sound), a REPEATER (a device that receives and retransmits a signal), and a MIC (a microphone).