Open Wire Telephony

I saw an article recently that reminded me about the early days of telephone technology. The article talks about the barbed wire fences used to bring the first rudimentary communications links to the remote Texas Panhandle.

Telephony using insulated copper wires started to appear in cities in the U.S. in the decades following the invention of the telephone in 1876 by Alexander Graham Bell. Around the turn of the 20th century, engineers developed a technology that could carry telephone signals for a greater distance using large-gauge bare copper wires. The technology involved installing two side-by-side bare wires – one to communicate in each direction.

Engineers discovered that a properly insulated network bare wire would have minimal power loss even over great distances. Bell Long Lines undertook the stringing of open wire copper routes on tall poles to routes between cities. The physical network consisted of bare copper wires connected at each pole to glass insulators. When I broke into the industry in the 1970s, I think every telephone technician and engineer had a green glass insulator sitting on their desk.

The cost of building poles and installing copper wires was expensive, and Bell Long Lines recovered its investment by providing expensive long-distance calls that generated enough revenue to justify building the network. Long-distance rates to call from coast to coast at the start of the 20th Century were around $1 per minute – adjusted for inflation, that’s over $33 per minute in today’s dollars. Only corporations, the very rich, or the government could afford to make long-distance calls in the early days of telephony.

The article talks about how the ranchers at the XIT ranch in Texas got creative and installed the technology using existing strands of barbed wire. The XIT ranch was gigantic and enclosed three million acres of grazing land. To provide context, the northern border of the ranch was 162 miles long. The quality of the connections using barbed wire was expectedly dreadful, but the connections were good enough to notify other parts of the ranch about emergency situations like a grass fire. The article says the ranchers tinkered and improved the quality of the barbed wire network over time by adding insulators along the fence to minimize the wire touching any surfaces that added interference. Early in my career as a consultant, I visited the XIT Rural Telephone Cooperative, and I remember seeing insulators along barbed wire fences. They were no longer used for telephony, and I never made the connection at the time to understand that the fences had been rudimentary telephone lines.

The technology for using open wire networks improved over time with the introduction of open wire carrier which used frequency division multiplexing. First-generation open wire carrier could carry up to 4 simultaneous calls on a pair of wires, and over time the carrier technology improved to carry up to sixteen calls at the same time on pair of open copper wires.

The use of open wire technology for long-haul transmission of telephone calls carried into the 1970s. Rural telephone companies built last-mile telephone systems using the traditional twisted-pair copper wires. But open wire technology was still the preferred way to send telephone signals for longer distances, and there was always one or more routes leaving a rural telephone exchange that used upon wire technology. These routes were always easy to spot due to the insulators.

The technology lasted even longer for railroads who strung long-haul copper networks between stations so they could have free calling. I wouldn’t be shocked if there are still a few of these routes in place along rural railroad spurs in the remote west.

Open wire technology was ultimately replaced by better technologies using traditional copper wiring, microwave radios, and ultimately by fiber. But many rural telephone companies kept the old open wire routes in place as an emergency backup for times when other wires went out of service.

I’m prompted to write blogs about older telco technologies when I occasionally ponder how far the world of communications has come in a relatively short time. We went from open wires to satellites and fiber optics in less than a century – largely thanks to Bell Labs, which constantly pushed the frontiers of how we communicate. I wonder what the folks at the XIT Ranch of 1900 would make of the 10-gigabit fiber routes that likely serve the area today?

2 thoughts on “Open Wire Telephony

  1. I enjoyed reading your article on Open Wire Telephony. It reminded me of the old days, as I started in the industry in the 70’s also. There is one paragraph where you referred to working 4 circuits over a pair of wires, I had an old friend who worked with open wire in the day who explained how it work to me, he referred to it as a Phantom circuit. I was always impressed with how much they could do with what they had.

    Donnie Kee

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