[SI-LIST] Re: Differential signaling history
- From: "Ingraham, Andrew" <Andrew.Ingraham@xxxxxx>
- To: <xlzhou@xxxxxxxxx>
- Date: Wed, 5 Mar 2003 10:45:41 -0500
For that, you probably need to go back to the beginnings of the
telephone. Perhaps even the telegraph.
Single-ended phone circuits over long distances with a common "ground"
simply don't work. Far too much noise.
You need two wires to complete a circuit, and if neither one is ground,
you logically get a differential pair.
They realized back then that the pairs had to be kept well balanced. On
old open wire telephone lines that used to run down highways or
alongside train tracks, you'd see that they periodically swapped the
wires in each pair (at prescribed intervals) to maintain balance and
cancel coupling between all the pairs and from other sources.
Regards,
Andy
> I am curious about the history of differential signaling. We can
> easily =
> explain in various versions intuitively or mathematically the benefits
> =
> of differential signaling now either in circuit design (differential =
> amplifiers/also called differential pair, for example) or in PCB
> design =
> (differential pairs), even in cable designs. What the first guys who
> =
> came up this idea originally thought and how/when they implemented the
> =
> idea ? etc.
>
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