How is a TV signal broadcast over the air?

Since June 2009, all over-the-air television stations in the US have been required to broadcast their signals in binary, or digital, form. That means they convert both the visual and the audio components of the television signal into sequences of ones and zeros, known as bits, before transmitting them over the air to your TV. A digital converter inside your TV then converts all those ones and zeros back into pictures and sound. Digital TV signals are similar to those broadcast by AM radio: The strength (or amplitude) of the TV signal is varied (modulated) to create the ones and zeros—that’s why it’s called amplitude modulation, or AM for short.

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