On Saturday, February 6, 2016 at 3:37:53 PM UTC-5, Jim Wilkins wrote:
"Ignoramus14059" wrote in
message ...
On 2016-02-06, Jim Wilkins wrote:


I often look at all that stuff, and I find extreme ingenuity with
which people overcame limitations of their current technologies, it
is
fascinating.

i

Tbe one that impresses me most is the old analog telephone which does
everything over two wires without active electronics, only one very
clever transformer, speaker and carbon mike. I couldn't quickly find a
circuit description and should return to fixing my fallen TV antenna
that had me abseiling down the snow-covered roof.

-jsw

The truly amazing thing is that all this stuff is still compatible. You can take your WECO 500 and plug it into your FIOS connected house, and it'll work fine, or you can plug it into your DSL line (with a filter) and it'll work fine. That they have maintained compatibility pretty much since day one is a testament to good engineering, and it's no accident.

I spent a few weeks several years ago working in the lab at Bell Labs. There, in a huge room (taking up several floors) they have pretty much every piece of phone infrastructure ever made. You can hook your device-under-test to hundreds of different phones, dozens of different switches and many, many interface, line balancing and protection devices. I was there qualifying and writing test procedures for interface devices for Lucent DSLAMs.

It's a truly interesting place and what amounts to a "living museum" full of very smart people, most of whom don't have a clue which end of a soldering iron to pick up. But they can jam many megabits per second through copper pairs, and 40 years ago that was deemed "impossible."