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Author Topic: Historical perspective on digital equalization (multi-tap filters)  (Read 894 times)

Scott Holtzman

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One of the many things I take pleasure in is placing technology in historical perspective.  While we think of things as new often times they are new applications for existing technology.  Much of the work we do is refinement rather than discovery.

I was reading through the archives of Bell Labs and came upon this article.  The author was trying to improve digital filters for MODEM's.  and important task in 1979 when 1200 baud was ripping fast. 

What is being discussed is an implementation of what we now call FIR filters.  Excellent examples of cumulative delay are given.

I thought some of you may enjoy the read:

https://archive.org/stream/bstj58-2-301#page/n0/mode/2up

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Scott AKA "Skyking" Holtzman
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John Roberts {JR}

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #1 on: October 12, 2017, 06:02:41 pm »

Bell labs is where a lot of milestone technology was pioneered (Guys like Shannon and Schafer, and.....) Those were the good old days.

JR
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Scott Holtzman

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #2 on: October 12, 2017, 06:10:18 pm »

Bell labs is where a lot of milestone technology was pioneered (Guys like Shannon and Schafer, and.....) Those were the good old days.

JR

Claude Shannon and Harry Nyquist defined the fundamentals of information transmission before digital computers existed.

The North American Digital Hierarchy that formed the TDM PCM telephone network was designed in the 50's based on these principles.

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Scott AKA "Skyking" Holtzman
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Ivan Beaver

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #3 on: October 13, 2017, 07:42:52 am »

Bell labs is where a lot of milestone technology was pioneered (Guys like Shannon and Schafer, and.....) Those were the good old days.

JR
Yeah-back when companies were allowed to make a decent profit, they could have whole sections (bell labs) where engineers could just "think" and not have the pressure to produce products.

A LOT of innovations in our industry came out of Bell labs.  So many things we take for granted today.
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John Roberts {JR}

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #4 on: October 13, 2017, 09:03:41 am »

Yeah-back when companies were allowed to make a decent profit, they could have whole sections (bell labs) where engineers could just "think" and not have the pressure to produce products.

A LOT of innovations in our industry came out of Bell labs.  So many things we take for granted today.
Bell was broken up for anti-trust reasons. Some of the baby bell companies reassembled but completely different industry today.

JR
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Hayden J. Nebus

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #5 on: October 25, 2017, 08:45:11 pm »

Oh, the irony!

I grew up in Monmouth County NJ. The local shed, once called the Garden State Arts Center, was built in Bell Labs backyard.

The best HOW service calls usually involved some combination of mangled graphics and piss poor gain structure that was done with the best of intentions, but invariably involved the proud hack work of a volunteer who was AN ENGINEER AT BELL LABS!
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John Roberts {JR}

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #6 on: October 25, 2017, 09:59:48 pm »

Oh, the irony!

I grew up in Monmouth County NJ. The local shed, once called the Garden State Arts Center, was built in Bell Labs backyard.

The best HOW service calls usually involved some combination of mangled graphics and piss poor gain structure that was done with the best of intentions, but invariably involved the proud hack work of a volunteer who was AN ENGINEER AT BELL LABS!
Maybe you could have gone to the labs and straightened them out.  ::)

JR
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Hayden J. Nebus

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #7 on: October 25, 2017, 10:45:34 pm »

Maybe you could have gone to the labs and straightened them out.  ::)

JR

Could have straightened out their graphic EQs at least.
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Scott Holtzman

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #8 on: October 26, 2017, 12:08:47 am »

Could have straightened out their graphic EQs at least.

Geez between Whippany and Murray Hill there were over 10k engineers in the hayday.   Maybe all didn't get audio.  Or maybe this was after the great Lucent "flaming asshole" transition.

Anyway if you worked in an engineering role @ BL prior to the MFJ that's pretty fucking awesome in my book.

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Scott AKA "Skyking" Holtzman
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Steve M Smith

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Re: Historical perspective on digital equalization (multi-tap filters)
« Reply #9 on: October 26, 2017, 06:24:11 am »

Yeah-back when companies were allowed to make a decent profit, they could have whole sections (bell labs) where engineers could just "think" and not have the pressure to produce products.

Some companies also had departments which seemed to have nothing to do with their business model.

e.g. One of Britain's great audio designers and authors, particularly in the hi-fi field (including class A amplifiers and various filters) was John Linsley-Hood who worked in the research department of British Cellophane Ltd.


Steve.
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