[TheForge] Re: Price of steel & scrap OT OT OT OT OT OT OT

[Andy Vida]

Bruce Freeman wrote:
> 
> However, digital computers will probably never equal the
> speed of analog.

	Never say never.  

	Analog is, though, very fast indeed.  Broadband internet
	connections are analog signals upon which the digital
	signals ride.  The nice thing about analog carrier is that
	you can do what's called Wave Division Multiplexing (WDM), 
	which allows you to run many "pipes" down a single "wire" 
	at once.  The same is done with optical fiber where a
	hundred or more separate data streams, each on it's own
	optical carrier frequency, can run down the fiber at once.
	A true digital carrier system can only do Time Division
	Multiplexing (TDM). Only a single stream can go down the
	pipe at a time, which is very inefficient.  But this is
	what drove the research into higher and higher digital
	bandwidths, resulting in the invention of the basic PCM
	data speeds, DS-0 through DS-7, zero being a 64KB/sec
	channel, 24 of which are TDM'd into a DS-1 (1.544 MBS T1)
	which in turn can be TDM'd with 27 others into a DS-3
	(~45 MBS, AKA "T45" or erroneously as "T3") and so on
	up to a DS-7, which is as I recall about 1.2 GBS.  The
	DS-5 was the first WDM technology developed and it was
	with a true digital carrier, unlike broadband.  It 
	was a 2" diameter microwave conduit through which a
	theoretically unlimited number of 474 MBS carriers
	could be run down.  The problem with the DS-5 lay in
	signal losses.  The inside of the copper conduit had
	to be perfect to 0.0001" in order to allow repeaters
	to be spaced at reasonable distances from each other.

	Anyhow, the development of WDM solved many of the 
	problems with squashing ever more information into 
	a given time slice.  Now you can run pretty well as 
	many concurrent streams of data down a single conduit 
	as you please.  There are limits, but every  year new
	ways are found to squeeze more and more streams onto
	a given carrier medium.  The technology is fablous.
	The genius that went into the conception and 
	formalization of technologies such as PCM (Pulse Code
	Modulation) is literally staggering.  The signaling
	schemes are in some cases so subtle as to almost
	defy belief.  Do a lookup of "robbed bit signaling"
	for just one example of the incredible creative genius 
	that went into the development of technologies we take
	very much for granted these days.  I've been in the
	biz almost 20 years and it still impresses me when I
	get to thinking about it.