[sf-lug] (semi?-)OT[1] - nice peek at some older[2] telephony technology (SF)[3]

[Michael Paoli]

So, ... heard of phone company CO[4]s? ... you know, where all the
POTS[5] (okay, they often include ISDN[6] and DSL[7], etc.) copper
pairs[8] come together from blocks or miles around, and go into the
beginnings of the telephone company's switching equipment?  Perhaps
you've even heard of or been to the Pacific Bell Museum[9] in San
Francisco?  How about a CO?  Heard of them?  Maybe seen some pictures?
But (at least for most) probably never been in one, or had a peek into
one?  How 'bout a peek in the window even?  (okay, so most of the newer
ones probably don't have windows).

Well, for a rather interesting peek ... through the window ...  in San
Francisco, right around 444 Bush St. - between the 444 Bush St.
entrance, and an historic San Francisco Engine Co. no. 2 (just up from
it on the same block ... okay, so that's mostly gutted and redone, but
at least some of the front is apparently preserved) ... anyway, if one
happens to notice, between the two ... glass windows, ... vertical
blinds, ... a slat or two or three missing among the vertical blinds,
...  have a casual peek through the missing slats, and one will see:
tightly packed rows, floor to ceiling - about 20 ft. from floor to
ceiling - rolling ladders like one might see in some densely packed
stacks ... basically "walls" that aren't walls, but floor to ceiling
racking of cable and cable termination points, with the cables rising up
and routed to their respective termination points; numerical labeling on
the racks to avoid confusion about which rack of probably about 50,000
or more termination points per side.  Large numbers of bundles of fat
multi-conductor cables coming up from below - rather massive in
aggregate size as they come up from below, thinning more and more up
the racks as they each branch out to their respective termination
points.  Anyway, makes for a fairly interesting peek through the window.

I'd don't know precise history of the building or the CO within, but
I'd guestimate that what one sees through that window is mostly
still-in-use technology that was probably built out there in somewhere
between the mid to late 1950s and about mid 1970s.  The switches and
such that the copper pairs connect to are likely *much* more modernized
than what must have originally been in that building ... but from my
fairly quick peek, I didn't notice anything that appeared to be actual
switching equipment.

Anyway, makes for a fairly interesting peek (at least until they fix
their blinds).

Footnotes/references:
1. OT - Off Topic
2. older, yes, but likely still in quite active use
3. SF - San Francisco
4. CO - Central Office
5. POTS - Plain Old Telephone Service
6. ISDN - Integrated Services Digital Network
7. DSL - Digital Subscriber Line
8. copper pairs - the pairs of generally twisted insulated copper wires
9. Pacific Bell Museum - 140 New Montgomery St. (been a few years since
   I was there, so not sure it's still there or still called that)