There’s this tv trope where the police try to track the origins of a kidnappers phone call, but this tracking operation requires time so they try to keep the kidnappers on the phone as long as possible to successfully conduct the trace. Invariably, the kidnappers hang up a couple seconds before they’re able to successfully identify the call location.
would today’s technology make this ‘keep them on the phone’ process quite unnecessary? Wouldn’t there be some sort of log somewhere for all incoming calls?
Today they have the information instantly available, for as much good as that does.
911 service knows where you are calling from, if you are calling from a land line. Things are more complicated with cell phones, but still doable.
VOIP makes things more challenging, as shown by the glut of robocallers. I don’t know how possible it is to trace one of those to the source with limitless resources (e.g. a kidnapper calls the family and the police try to find where the VOIP phone is located), but it is certainly a barrier to finding scammers.
Everything was handled through mechanical switches that eventually went to a trunk line to…somewhere else with more switches. A trace would involve a technician going into the depths of the central office and tracing switch positions for each digit.
ETA: In the UK things were somewhat different, you could hold the line open by not hanging up your end. If someone called you and you never hung up, the circuit would remain open all the way back to their phone, and they wouldn’t be able to disconnect it.
When I was a child I snuck into a building that was filled with such a switching system. It wasn’t so much a “central office” as it was a large, tall windowless, anonymous structure, with a small parking lot for utility trucks. (The back door wasn’t locked.) It was a holiday and I didn’t see a single person inside–just all of the huge banks of switches clicking and moving like in that video, causing a general din. I tried to find where my family’s phone number would be but couldn’t figure out the system.
Later I went back to go in again and they’d locked the back door. So I went to the front door and rang the bell. When someone opened, I said I was interested in telephones and asked if they gave “tours.” It turned out that they’d discovered someone had gone in (they said a neighbor had seen me), but I suspect they might have had CCTV. When they confronted me about that I somehow convinced them to still give me a “tour.” I guess they were flattered that an 8-year-old was interested in what they did in this anonymous building that otherwise went completely ignored by the public. They showed me the switch of my family’s phone number.
What I’d like to know now is this: What do they have now in that space? When I return to my childhood neighborhood I see the phone company still owns and does something in that building. But what did they do with all those switches? What occupies all that space now? What was the process for making the transition at a site like that?
That building is a “central office” aka a public exchange. These are generally non-descript and their locations are not advertised by the phone company.
It depends on the timeframe, but honestly the guts of it probably haven’t changed much at least in function, but they will have likely have fairly modern hardware, handling additional stuff like DSL. Most of what we call “land-lines” today are handled through either fiber optic or cable and do not use a central office.
One of the colocation facilities our company used had large sections blocked off for telecommunications companies, so in those cases it’s going to look a lot like a huge server room in some huge building with tons of racks, because that’s basically what it is.
Well, they still have all the wires coming in there.
Remember that every landline (or building that formerly had a landline) has a pair of copper wires running uninterrupted from that location back to the Central Office (plus a bunch of spares), and that every cell phone tower has cabling for 240-300 calls back to the Central Office. And those are mostly copper pairs that were installed decades ago (and are still working) – those wires haven’t gotten any smaller, and they all need to connect to the Central Office switching system.
Now the switching system is an electronic switching system (really, one or more computers) which is much smaller and more efficient than the old mechanical switches. But it still takes up a lot of space, especially when it needs to be kept cool and easily accessible for quick repairs. Plus the ‘phone system’ does a whole lot more functions than in the old days, which requires more equipment.
Also, it is no longer one-company monolithic phone system. There are many ‘phone companies’, and many secondary phone providers, who lease their physical lines from other phone companies. Many of these secondary companies rent some vacant space in Central Office buildings, where the old mechanical switches were.
So most of the ‘phone system’ work is still done in “large, tall windowless, anonymous” Central Office buildings – it’s just done via electronic equipment, often by multiple different ‘phone companies’.
What happened to the switches? They got recycled. Western Electric and AT&T were probably the largest consumers of precious metals until the 80s as those switches were filled with platinum contacts, gold plating, and of course, all that copper wire.
Depending on the region and the incumbent carrier, a “central office” may look more like a datacenter than a phone company as the days of individual copper pairs running from the CO to your home are fading away. My phone lines are copper for about three blocks until they get to a thing called a VRAD (Video Ready Access Device) as this is AT&T country and they still have their Uverse internet-phone-TV service. Connecting the VRAD to the CO is fiber, not copper. Said fiber is carrying my neighborhood’s phone lines, internet, and 700 or so TV channels as a whole lot of bits. At the CO, the various neighborhood fibers plug into network switches that sort out the TV, data, and voice lines and route them appropriately on AT&T’s backbone.
The equipment that does this is tiny compared to the old days of thousands of copper pairs*, so some carriers set up colocation facilities and sell space with fast connections directly into that backbone.
And the equipment that the fibers replaced was tiny compared to the old crossbar switches. Starting in the early 80s, AT&T ripped out building-filling step-by step and crossbar systems across the country and replaced them with the 5ESS electronic switching system which was run by a 3B20 mainframe that could fit on a trailer and be rolled into the building after the cutover was done and space cleared in a process called a “hot slide.”
pre-ample:
At one time, the phone switching systems were electro-mechanical and worked on relays. It would take time for someone at the phone company to manually trace the call which needed coordination across the switching offices.
The function of these switching systems were moved to computer running a real-time version of the UNIX operating system called DMERT developed at Bell Labs. They developed ANI (Automatic Number Identification) system, which is what became Caller ID. This is long before Caller ID was available. But I can tell you, some smaller phone companies after the break-up of Ma Bell in 1984, still had some of these electro-mechanical at in the field in use as late as 1987 or 88. I know because I physically saw them. Local system switches already on their way of being replaced by 5ESS computers.
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To answer your questions:**
Yes, in 2020 this story plot is no longer valid. However, they still use a variation of this but with cell phones and supposedly do some sort of triangulation of the signal between cell phone towers and get a location of where the call is coming from physically. Although I wouldn’t be surprised if a data packet using the GPS in the cell phone is included in what might be the CCS7 messages for use by law enforcement and 911 emergencies.
Yes, it was a real thing at one time before it went to computer in the 1970s/80s. But even as late as 1987/88 this was still valid with small phone companies still using mature technology. But I recall seeing some movies and TV stories with landlines where they instructured the character, “Keep him on the phone as long as possible” so they could trace the call. I use to laugh at those, because whoever approved this screenplay was out of date with technology.
Those offices now have local switching systems which run on a computer. The old ones likely ended up as landfill. The rest of the space there have administrative offices.
The place with the relays was called the Central Office because once upon a time it was filled with operators (teen-age boys at first then women when the boys didn’t work out so good) who would connect your call manually. Eventually the women were replaced by machines that could handle connecting local calls then much later in a technical triumph by Bell, could also handle connecting long distance calls – the last was a lot more complicated than you’d think.
Back in those care-free days the Western Electric engineers were really proud of their accomplishment so the details of the systems’ innermost workings were freely available in libraries. This is what let the phone phreaks and others exploit the system for their own amusement in the former, more nefarious purposes in the latter.
This book goes into great, fascinating detail on the subject if you like that sort of thing.
Full disclosure: I know the author. In the unlikely event you contact him, tell him Kitsune says hi.
Those buildings are now used to intercept all of your communications, record them and forward them to Facebook, Google, Amazon and, of course, the Deep State.
Another trope is phones being tapped by placing a device in the phone or on some equipment in the basement. Old style landline phones could be tapped from locations some distance form the target. No need to get into the house or building to do it.
I’ve read in previous threads here that Ma Bell and the rest expected switching technology to get smaller. But they didn’t correctly estimate just how much smaller. Public exchanges now have empty spaces the size of football fields.
Re Tapping
IIRC The film Blowout has somebody tapping a phone with a standard set of earphones and a wire ending in an alligator clip. Again IIRC, this would have actually worked at the time.
The wonderful book The Mueller Fokker Effect* has somebody tap a phone at the street using this method. The intended target, already paranoid, hears a ping which warns him of the tap. I’m curious to know if that bit is accurate.
*I’d like to get some Christian friends to read it. Besides being a great book and well worth sharing, it’s full of Christian allegories and subtle references. OTOMH Reverend Billy, Shairp, and (Blast I can’t remember the name of the virgin publisher of Stagman) are all stand ins for Jesus. All the significant female characters are named variants of Mary- Myra, Margery, etc.
Old-fashioned low-tech wiretaps using a linesman’s set could be heard if they were connected while you were on the line. There would be a “click” and maybe a slight reduction in volume when the connection was made.
I’ve done that in the exchange (or ‘central’ if you’re American - no doubt it’s German like so many Americanisms) and the parties did indeed remark on how the call volume had suddenly reduced. (And, no I didn’t spend any amount of time doing that, you quickly loose all curiosity about peoples’ phone calls when you work there all the time)
Many of the buildings in central London have been partly or wholly sold off where the value justifies it. Parts of WELbeck exchange have been turned into apartments. NATional was completely demolished and is a unit inside FARaday now. Part of FARaday itself has been leased to the Scientologists. In many others there is plenty of spare space.
Our sturdy house sat on a rocky outcrop over the Russian River. I was at home when the 1989 Loma Prieta quake interrupted the World Series and trashed many SF Bay Area structures. I felt nothing, though buildings in the gorge suffered damage. I only knew something had happened when the radio went silent. I called MrsRico in San Rafael (her office shook but no-one was hurt) and then DadRico in southern California to say we were OK. I couldn’t call out the next day. Our local phone office switches were so old, they took a whole day to fail!
Tracing calls was easy long ago. Just follow the strings between tin cans.
