A device for moving the frequency of an information signal, which is generally at baseband (such as an audio or instrumentation signal), to a higher frequency, by varying the amplitude of a mediating (carrier) signal. The motivation to modulate may be to shift the signal of interest from a frequency band (for example, the baseband, corresponding to zero frequency or dc) where electrical disturbances exist to another frequency band where the information signal will be subject to less electrical interference; to isolate the signal from shifts in the dc value, due to bias shifts with temperature or time of the characteristics of amplifiers, or other electronic circuits; or to prepare the information signal for transmission.