Ask Hackaday: With Landline Use In Decline, What’s To Be Done With The Local Loop?


Walking is great exercise, but it’s good for the mind too: it gives one time to observe and to think. At least that’s what I do on my daily walks, and being me, what I usually observe and think about is the local infrastructure along my route. Recently, I was surprised to see a number of telephone company cabinets lying open next to the sidewalk. Usually when you see an open box, there’s a telephone tech right there, working on the system. But these were wide open and unattended, which I thought was unusual.

I, of course, took the opportunity to check out the contents of these pedestals in detail. Looking at the hundreds of pairs of brightly colored wire all neatly terminated and obviously installed and maintained at great expense, I was left wondering why someone would leave such a valuable asset exposed to the elements. With traditional POTS, or plain old telephone service, on the decline, the world may no longer have much use for the millions of miles of copper cable feeding back to telco central offices (COs) anymore. But there’s got to be something this once-vital infrastructure is still good for, leading me to ask: what’s to be done with the local loop?

Inside Plant, with a Side of BORSCHT

Like any industry that’s been around since before the previous turn of the century, the telephone industry is rife with jargon. Telcos refer to all the things they use to run their systems as their physical plant. If this brings to mind the image of a factory, that’s not far off: the switchgear, cables, and supporting equipment really are a huge machine, and initially, telcos are really just factories built to move sound from one place to another.

Telco physical plant equipment can be divided into two broad categories: the inside plant and the outside plant. The inside plant is, as the name implies, everything that resides under a roof. This includes the switchgear itself, the main distribution frames where the incoming local loop wires are connected, plus all the support gear for so-called BORSCHT functions, an acronym for:

  • Battery (nominal 48 VDC to power the local loop);
  • Overvoltage protection from surges on the local loop;
  • Ringing voltage (about 89 V RMS);
  • Signaling or Supervision, which detects on- or off-hook conditions at the subscriber end and decodes DTMF tones;
  • Coding, which provides support for digital encoding and decoding algorithms;
  • Hybrid, which transforms the two-wire local loop into a four-wire connection;
  • and Testing, which allows field techs to connect a subscriber directly to testing gear in the central office.

Things tend to change within the inside plant fairly rapidly as technology advances. For example, many COs started out filled with either step-by-step (SxS) or crossbar switches, with rack after rack filled with sparking, clacking relays and solenoids that connected one subscriber line to another within the exchange, or shipped it off to another exchange for connection to one of its subscribers. Later, electronic switches came in and replaced all that old gear, and change that was often performed so quickly that subscribers barely noticed the changeover.

Outside Plant

Outside plant refers to everything the telephone company installs outside the central office. If it’s strung up on poles, buried in the ground, or sitting on a tower on a mountaintop somewhere, it counts as outside plant.

The most obvious bit of outside plant is the miles and miles of wire that form the local loop. In the early days of telephone service, and probably clear up to at least the 1980s or early 1990s in North America, the local loop was exactly that — a single pair of copper conductors stretching from the main distribution frames in the central office to the demarcation point at the subscriber’s premises. When a phone  was taken off the hook, the loop was completed and the process of making or taking a call began.

A telco pedestal for a condo in my area. This example of telco outside plant has been open to the elements for weeks.

Like the inside plant, the local loop and the other components of the outside plant changed over the years, with additional equipment added to handle newer digital technologies, like integrated services digital network (ISDN) and digital subscriber line (DSL). But despite the changing technology, a lot of what the telephone companies did to upgrade their services was predicated on leveraging their most valuable asset — all those miles and miles of precious copper, carefully crafted into a massive network reaching nearly every address on the map.

Sadly, though, there’s only so far you can push 19th-century technology, and telephone companies, already with their backs against the walls, faced a double challenge starting in the early 2000s: the rise of the cell phone and the emergence of widespread broadband. No longer were people tied to a landline, when a cell phone could do the same job and more. And in those cases where cell coverage was poor, chances were good that a broadband connection could be leveraged with one of the new VOIP telephone services, piped into the subscriber’s premises either via a cable internet provider or, ironically, over a DSL connection.

Sign of the times: Ziply fiber is coming to town. Source: Ziply Fiber

But the surge in DSL connections was really a last hurrah for the copper local loop. Fixed landline subscriptions have fallen in the US since 2000 from nearly 200 million (about 70% of the population at the time) to only 116 million lines in 2018. People just don’t have a valid use case for a landline phone anymore. This explains the specifics of my observations during my morning walk: a few days ago, a cable construction crew showed up near one of the pedestals I found open and set up a signboard announcing the arrival of a new fiber-optic network by Ziply. It turns out that Ziply bought the operations and assets of Frontier Communications in my area back in May, and are investing $500 million to upgrade the network.

Your Turn

From what I’ve seen, Ziply is primarily interested in leveraging the rights-of-way of the outside plant they inherited from Frontier. Those few remaining landlines seem to be little more than a source of cash to finance the build-out of their new network. My question is: what’s to become of all those copper lines?

It seems a shame to just abandon such a valuable asset in place, but maybe it only seems valuable to someone who isn’t running a fiber-optic company. Perhaps all the copper will one day prove to be just a nuisance, something to suck up maintenance budget while returning little value. Maybe at that point it would make sense to scrap it — pull all those carefully installed and slavishly maintained cables off the poles and out of the conduits and sell it off for its scrap copper value.

Or is there perhaps another plan for such a seemingly valuable asset? Could copper networks still have a place in the communications ecosystem, one that takes advantage of their unique position of connecting virtually every home and business? We’d love to hear your thoughts on what’s to be done with the local loop, and we’d especially love to hear from any of the telco engineers who devoted their careers to building these amazing networks and keeping them alive. There have to be a ton of inside stories about the outside plant, and we’d appreciate you sharing them in the comments below.

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