Changes

:Regularly undulating voltages are also used for all forms of electromagnetic transmission—radio, television, cell phone, etc.  In this case the frequency is often measured in [[Metric_system|Megahertz]] or Gigahertz.

:Regularly undulating voltages are also used for all forms of electromagnetic transmission—radio, television, cell phone, etc.  In this case the frequency is often measured in [[Metric_system|Megahertz]] or Gigahertz.

*Any type of varying signal, such as an audio signal, is often characterized as "AC".  Audio signals don't generally have a specific frequency, they are described as being contained in a "band" of frequencies, but they are still called AC.  If the long-term average voltage of a signal is nonzero, that average is often called the "DC component", while the signal with the DC component subtracted is called the "AC component".

*Any type of varying signal, such as an audio signal, is often characterized as "AC".  Audio signals don't generally have a specific frequency, they are described as being contained in a "band" of frequencies, but they are still called AC.  If the long-term average voltage of a signal is nonzero, that average is often called the "DC component", while the signal with the DC component subtracted is called the "AC component".

==References==

==References==