A better name for them is perhaps utility poles — which is what some people already call them. The repair costs are immense, as is the disruption for people living nearby. By relocating lines to protected tunnels below the earth, some think we could tidy up the nation and safeguard our utilities network.
The cheapest is open trenching. This involves digging into the earth, laying down large stretches of cabling and backfilling the trenches later. None of which is usually welcomed by the communities affected. The second approach is called directional drilling. This approach — a new take on an old technique for drilling oil and gas — is much less invasive. However, this approach is incredibly expensive. Not ideal. So, while undergrounding sounds like a good idea on paper, the process is disruptive and costly.
We are on the cusp of 5G — the fifth generation of mobile technology. This has led some to speculate that the technology could be used to replace our wired broadband connections.
So, will 5G usher in the end for telephone poles? For one thing, as mentioned above, telephone poles are used to support a variety of other utilities — not just telephone lines. In October , Dr. Vacuum tubes were the first electronic devices.
The audion in particular could be used to manipulate an electric current by use of a second current passing through the grid, the central element of the three. It could produce a small amount of amplification but, beyond that, the tube gave off a blue glow, and amplification ceased. Arnold quickly resolved the problem. The blue glow was caused by the electrons interacting with the residual gas in the tube.
While de Forest thought the residual ions were necessary for the proper operation of the tube, Arnold believed, correctly, that if he could increase the vacuum, the device would amplify signals more powerfully for the life of the device. The transcontinental line now became a construction project to connect Denver with the separate West Coast network. By , all of the loading coils on this line had been replaced by an additional nine repeaters, and with this change the bandwidth doubled, and the sound quality improved.
Vacuum tubes led to many additional improvements in transmission. Used as modulators, tubes made it possible to increase capacity by employing what were called carrier circuits. While existing circuits could carry just one signal down a wire pair at voice frequencies, a carrier circuit could send multiple signals down a single circuit, using several simple waves fixed at a series of higher frequencies, and modulating these waves with the sound frequency waves carrying the conversations.
This technique became known as multiplexing. It provided four additional multiplexed channels on each wire pair, and used vacuum tubes both as modulators and repeaters.
By its peak of application in the early s, over 1. With great distances, and relatively low volume on most routes, the majority of long distance lines in the United States through the s and s were carrier circuits on open wires. Long distance cable was used only on a smaller number of high volume routes. In Europe, by contrast, in , 84 percent of long distance circuits ran through cables.
With a few minor exceptions, these cables did not use carrier circuits. In addition to telephone conversations, many long distance circuits throughout the world carried radio programming between radio stations. Among the notable lines built elsewhere in the world was one opened in South America in that crossed the Andes to connect Buenos Aires, Argentina and Santiago, Chile.
Radio itself was used for circuits where there was no alternative, notably to provide for transoceanic communications. Telephone service opened between the United States and Great Britain in over a long-wave radio circuit, connected to the conventional wired networks at both ends.
Over the next few years, both long- and short-wave circuits were used. In the s, experiments foreshadowing the beginning of television transmission which would require transmission bandwidths in megahertz rather than kilohertz and capacity concerns on a few long-distance routes led to a search for a broader bandwidth, higher capacity, transmission medium.
In Great Britain C. Patent 1,, in They reduced to practice theoretical work done by several scientists, including Oliver Heaviside and Lord Raleigh, many years before that showed a system consisting of a central conducting wire centered in a conducting tube could carry an enormous signal bandwidth. The signals would be contained between the outer surface of the central core, and the inner surface of the tube.
Espenschied and Affel designed a workable system, with appropriately sized copper wires and tubes, held in concentric symmetry by spaced dielectric washers, with signal strength retained with repeaters. Additionally, such a cable was by nature self-shielding, and resistant to interference, since the signal was on the inside surface of the concentric conductor.
Bell Labs successfully tested the concept in , and in installed a semi-commercial, repeatered, coaxial cable system with one tube for each direction between New York and Philadelphia, capable of carrying conversations or a single television channel. Bell Labs next designed an improved system, with four redesigned tubes in the cable, capable of carrying calls or a 4 MHz television channel. After the war, construction of coaxial cable lines resumed. By over 5, route miles of L-1 coaxial cable were in service, providing telephone circuits and television networking facilities along the east coast and west to Chicago and St.
Three improved and still higher capacity systems followed, culminating in the L-5 system in the s, which had 22 tubes, and a total capacity of , telephone calls.
By , L-5 Systems provided almost 66 million voice-miles of capacity in the United States. In the , a joint U. With the spread of these deep sea cables, the earlier transoceanic radio circuits were abandoned.
Two German companies joined to develop and manufacture coaxial cable for the German government. After several shorter tests, a channel, long-distance, coaxial cable entered service between Berlin and Leipzig in In Britain, a channel coaxial cable opened between London and Birmingham in , and a submarine coaxial cable to the Netherlands the following year. Three years later, this cable was connected to a new submarine cable between Nakhodka and Naoetsu, Japan, providing a direct cable route from Europe to Japan.
While there had been several experiments in the s on using microwave radio as a telephone transmission medium, practical development began only with the invention of the klystron, a practical microwave amplifier, by Russell and Sigurd Varian at Stanford University in Intense development proceeded throughout World War II, and led to a second transmission system with the high capacity needed for increased telephone volume and television. As early as , Bell Labs began planning for such a system, connecting New York and Boston with a series of seven microwave-radio relay towers between the two cities.
Construction of this TDX trial system began in , and the system went into successful commercial operation in It connected to a new coaxial cable between New York and Washington to provide television transmission facilities connecting stations along its route. It carried four channels at different frequencies around four GHz. Each channel could carry telephone circuits or one television signal. In this, as in subsequent systems, voice or television was carried as modulation of carrier microwaves, which were transmitted between towers over line-of-site routes.
The towers, at least on this first route, were placed on hills. Microwave relay had several advantages over coaxial cable: quicker construction, easier construction in difficult terrain, and no need to acquire a continuous right of way from property owners along the route.
Louis to the west coast. As solid-state devices replaced vacuum tubes in the TD-2 system in the s, the number of circuits per channel increased to in By the mids, microwave relay systems had been employed throughout the world, wherever terrain or required speed of construction limited the use of cable.
Ministers are also asking whether access to broadband should become a legal right, like water and electricity, in order to prevent a rural versus urban digital divide. In the UK, every home and business is entitled to a telephone line and dial-up internet access, but not broadband. The government has a universal service commitment USC , which is not legally binding, to deliver a minimum broadband speed of 2Mbps to every premises.
The consultation paper asks: "Is there a role for a revised USO or USC to ensure that minimum consumer demand requirements are met and to reduce the potential for a new digital divide?
What might this look like? Painting a picture of digital Britain from to , the ministry sets out three potential future scenarios. Under the first, demand for fast internet is modest. Under the third, demand is at the upper end of current forecasts. Outlining scenario three, the paper imagines voice traffic will be carried mainly over mobile phones, with the fixed line connection reserved for internet access.
Home working will become more popular as the difference between networks for homes and small businesses blurs. Both will have access to lightning-fast 1Gbps speeds that allow content to be uploaded as rapidly as it is downloaded.
0コメント