Telephone Company Central Offices ("C.O.'s")
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[
https://en.wikipedia.org/wiki/GTE]
Picking up where I last left off, which was Jack taking Steve and I "trashing"
at our first telephone company "Central Office" or "C.O." building. This would
likely have been around 1995 or maybe 1996 at the absolute latest.
Before talking about what we found trashing that night, I think that a
digression on telephone company Central Office (CO) buildings is in order. I'll
write about the lucrative dumpster contents from our first night trashing in a
future Gopher article.
COs are almost always large, brick, non-descript, windowless buildings scattered
throughout a city, or very sparsely scattered throughout more rural areas. In
every case that I know of, the buildings will have the telephone company name
and/or logo affixed to them. Other telltale signs of a CO may include a
chain-link fence (GTE never, ever seemed to lock theirs), telephone company
vehicles parked outside, large diesel generators, and the rapid appearance of
many manhole covers as one gets closer and closer to the building. You have
likely driven past many of these buildings and yet never noticed that they were
there.
[By the way, GTE (or General Telephone) merged with Bell Atlantic in the early
2000s to make one of the world's largest telecommunications companies: Verizon.]
Here are a few Web sites dedicated to photographs of Central Offices:
http://www.co-buildings.com/
https://www.thecentraloffice.com/
First and foremost, I want to say that COs are far from irrelevant today. (And
yes, I'm biased and nolstagic and *want* COs to still be relevant, but really,
they still are incredibly relevant, just in a different way from when I was
first skulking around outside of them in the middle of the night.) While it is
true that many of them are being transformed into "data centers", part of the
Internet "Cloud", and so on and so forth, it is also true that they remain at
the core of today's wireless telecommunications system. You likely know that
your "smartphone" wirelessly connects ("by radio") to one or more nearby "cell
towers" in order to get its "signal." But what do the cell towers in turn
connect to? Is the cellular telecommunications system simply made up of a
massive number of directly interconnected cell towers or is there some larger
aspect to this infrastructure?
In short, the cell towers all make their way back to some nearby building called
the Mobile Telephone Switching Office (MTSO). The MTSOs are in turn connected
to nearby COs, which are in turn connected to the worldwide Public Switched
Telephone Network (PSTN). You can kind of think of the PSTN as the global
telecommunications "cloud", in today's silly parlance. Basically it is a
stand-in for a massive interconnected network of telecommunications elements,
systems, and sub-networks that deliver voice and telecommunications-related data
(SMS, etc) around the globe. COs remain the primary "on-ramps" and "off-ramps"
to and from the PSTN.
Obligatory shitty ASCII diagram:
________________________________________________________________________________
| |
| "Smartphone": Alice <-> Cell tower <-> MTSO <-> CO |
| | |
| | |
| | .-~~~-. |
| .- ~ ~-( )_ _ |
| / ~ -. |
| | PSTN ', |
| \ .' |
| ~- ._ ,. ,.,.,., ,.. -~ |
| ASCII art "Cloud" | |
| | |
| | |
| "Smartphone": Bob <-> Cell tower <-> MTSO <-> CO |
| |
--------------------------------------------------------------------------------
Figure 1: Connecting Alice and Bob across town, across the state, across the
nation, or across the world
Okay, now that I have gotten my digression on the continuing relevance of COs
out of the way, we can get back to talking about COs as I knew them back in the
1990s.
As mentioned before, the CO buildings house the telephone switches, which are
basically specialized computers and electronic systems with upwards of hundreds
of thousands of pairs of copper wires coming into and out them, making up the
"Outside Plant" (OSP) of a particular CO's area of service. There are also
digital "trunk lines", typically interconnecting the various telephone switches
into a larger network. In fact, there are a heck of a lot of things coming in
and out of the CO but I think that focusing on analog land lines ("copper
pairs", "local loop") and digital trunks has been a pretty traditional approach.
Think of COs as a central part of the "nervous system" of the world's
telecommunications infrastructure.
Switches housed in the CO buildings we'd visit included the 5ESS switch by AT&T
(now Lucent Technologies), the DMS-100 switch by Northern Telecom (Nortel), a
Canadian company that lasted from 1895 until it filed for bankruptcy in 2013,
and the GTD-5 switch by AGCS (AT&T / GTE Communications Systems, originally the
GTD-5 EAX switch by GTE). The 5ESS switch still plays a major role in modern
cellular telecommunications in the form of the 5ESS 2000 Digital Cellular Switch
(DCS).
[Fabulous textfile on the 5ESS switch:
gopher://sdf.org/0/users/d1337/textfiles/PHRACK43_16_5ESS.txt]
Below the CO is the Cable Vault, where all of the cables coming in and out of
the building enter and exit. Hence all of the manhole covers surrounding most
COs. One CO we would regularly visit (late at night) must have always left the
lights on in the Cable Vault because we would always see light shining out of
holes in a manhole cover right next to the building and could peek through those
holes and see down into the Cable Vault. That was something really neat for us,
because the inside of the COs were like a mystical place that we figured we
would never get to see the inside of. One time I even rode my bicycle to a CO
near my house during the day and waited out front as telephone company people
came in and out of the building, asking them for a "tour." No such tour was
ever given on that day. (I would later get to tour a CO but it wasn't until I'd
long since given up my phone hacking days and was myself working for The
Telephone Company.)
In addition to the Cable Vault is the Main Distribution Frame (MDF). The MDF
serves as an indirection point between the Inside Plant, such as Line Equipment
(typically things like Line Cards that interface Plain Old Telephone Service
(POTS) copper pairs to the switch) and the Outside Plant, where each customer
line is typically supplied a Cable and Pair (for example, cable 6, pair 389).
Mappings are stored in a switch database that associate each Line Equipment
Number (LEN) with a Telephone Number (TN). This is kind of sort of like the
relationship between a MAC address (Line Equipment, fixed address number) and an
IP address (which can change association much more readily). Your telephone
number could be associated with one particular LEN today and moved to another
LEN tomorrow with no apparent effect to you or anyone else calling your phone
number. "Jumpers" are twisted pairs of copper wire that make the physical
association between the Line Equipment side of the MDF and the OSP side of the
MDF.
Finally, there are the computers, teletypes, switch control consoles, Read-Only
Printers (ROPs), and more. Of particular interest to telephone hackers were
finding dial-up phone numbers, usernames, and passwords that gave access to the
computers either stored in the CO or stored elsewhere but used by the CO on a
frequent basis. The teletypes and Read-Only Printers were great because their
sessions were necessarily committed to paper and very often found their way into
the CO dumpster, many times with dial-up phone numbers, usernames, passwords,
and inadvertent "how to" guides completely preserved. Obsessive semi-autistic
night time CO dumpster divers like Steve and I would hit up a large number of
COs each weekend, grabbing every comnputer or teletype print-out or discarded
manual that we could find and later inventorying and cataloging all of the
contents, building up over time our own "how to" guides, long lists of dial-up
phone numbers, usernames, passwords, and more.
I'll write more about these computers systems in-depth in a future Gopher
article.
Now why on Earth would a certain minority of mostly teenage boys be interested
in one of the central apsects of the world's telecommunications infrastructure?
Power? Being part of an "elite"? Mystique? Being in places where one is not
supposed to be? Being aware of important things that for so many others go
completely unnoticed? Probably some mixture of all of the above.
For Steve and I, it was almost certainly being part of an "elite", having
"powers" that others did not have, and having one hell of an interesting,
labyrinthian, and forbidden system to explore. We were mostly "Boy Scouts"
about the whole thing when it came to leaving things as we found them, not
damaging the system, not wearing out our welcome, and so on and so forth. Some
"phone hackers" took up an adversarial stance toward the telephone company; ours
was more of reverence.
By the way, in the "elite / underground BBS culture" that I've written about
previously on Gopher, the telephone system hackers were very close to the top of
the hierarchy of eliteness, if not *the* top of the hierarchy. That was
definitely something that Steve and I wanted to be a part of. The elite of the
elite.
CREATED 2023-04-10
