Paper cups, string, and electrical signals

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Photo by chefranden

Question: How can you transmit a signal down a wire. If it’s just binary, what use is the analog stuff?

Answer: Have you ever played telephone with two paper cups and a string? This article does a good job of explaining the game and how it relates to electrical signals:

A wire can carry a changing voltage. The speed of change and the magnitude of voltage are two ways varying information can be transmitted on a wire. With the invention of the microphone we have a direct way of converting sound to an electrical signal. The invention of the speaker converts the electrical signal back to sound.

Did I give you an intuitive feeling for how a signal can be more than on and off?

 Let’s try another way of thinking about it. If you play with the volume knob on your stereo you can modulate the sound with finer control than just on and off, one and zero. But what you are doing is slow. The signals for speech are faster. If you are already okay with the idea that the sound from your stereo speaker has varying voltages to move the speaker coil, much like your volume knob varied the loudness, then imagine really long speaker wire. The speaker wire is transmitting analog electrical signals.

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