IELTS Academic Reading Practice Test 201

For most of the nineteenth century, sending a message by telegraph required a skilled operator. The sender's words were converted into a code of short and long electrical pulses, and at the far end of the line another operator listened to the clicks and wrote the letters down. A message therefore passed through at least two trained pairs of hands before it reached the person it was addressed to, and mistakes were common. The teleprinter changed this. It resembled a heavy typewriter, and it allowed someone who could merely type to send a message that arrived at the other end already printed on paper.

The idea of a telegraph that printed its own messages was pursued almost as soon as the electric telegraph itself. In the 1840s and 1850s inventors in the United States and Britain, among them Royal Earl House and David Edward Hughes, built machines in which a keyboard at one end controlled a printing mechanism at the other. These devices were ingenious but complicated, and they were soon displaced by the simpler Morse system, whose single wire and trained listeners were cheap to operate. Printing telegraphy remained a curiosity for several decades, kept alive by a handful of engineers who believed that speed and accuracy would eventually matter more than simplicity.

The decisive figure was Émile Baudot, a French telegraph engineer. Working in the 1870s, Baudot designed a system in which every character was represented by a fixed pattern of five electrical signals, giving thirty-two possible combinations. That was fewer than an alphabet with figures and punctuation required, so he allotted the same codes to two different sets of characters and switched between them.

Baudot's other innovation was to let several operators share a single wire: each typed in turn for a fraction of a second, and the receiving machines separated the incoming signals by means of a rotating distributor. A line that had carried one message at a time could now carry four or more.

Baudot's code was refined by Donald Murray, a New Zealander working in Britain, who rearranged the assignment of codes so that the most frequently used letters needed the least work from the machinery, and who added control codes, such as those for a new line, that a printing machine needed. The resulting code was adopted as an international standard in the early twentieth century and remained in service for most of it. Murray's arrangement was designed to reduce wear on the equipment rather than to suit the typist, and the principle of a fixed-length code for each character passed from telegraphy into the design of computers.

A teleprinter of the kind that became familiar in offices was a robust electromechanical device. The operator typed on a keyboard; each keystroke was turned into a pattern of electrical pulses and sent down the line; the receiving machine decoded the pattern and printed the character on a roll of paper. Many models could also punch the same signals into a paper tape, which could be fed back into the machine later and transmitted at full speed with nobody at the keyboard. This mattered because it allowed messages to be prepared in advance and forwarded automatically, an idea that would reappear in the store-and-forward logic of computer networks.

From the 1930s the teleprinter became the basis of a public service. Germany introduced a switched network, known as Telex, in 1933, and other countries soon followed; a subscriber could dial another subscriber anywhere in the network and type directly to them. The machines transmitted at about fifty bits per second, roughly sixty words a minute, so a message was far slower than a telephone call. It nevertheless produced a written record at both ends, and it could be delivered to an office that was closed or in another time zone without anyone being there to answer. The telex number became, for many businesses, as familiar as a telephone number.

News agencies were among the earliest and most enthusiastic users. A reporter's copy could be typed into a teleprinter in one city and emerge minutes later in newspaper offices across a country, which helped to make national news simultaneous. Weather services distributed forecasts to airports in the same way, railway companies used private circuits to coordinate trains, and police forces exchanged descriptions of suspects. Because every message arrived as a typed document, teleprinter traffic also became evidence: transcripts were filed and quoted, and in some countries, accepted in courts.

The teleprinter's decline began in the 1980s. The fax machine could transmit a drawing, a signature or a page of handwriting, which the teleprinter's restricted character set could not, and the personal computer offered word processing and, before long, electronic mail. Telex survived longer than might be expected, particularly in shipping, insurance and parts of Africa and Asia, because a telex message carried a record of transmission that was legally useful and because the network kept working when other systems failed. Public telex services were closed one country after another in the early twenty-first century.

One offshoot proved unexpectedly durable. In the 1960s a deaf American physicist, Robert Weitbrecht, devised a coupler that allowed surplus teleprinters to communicate over ordinary telephone lines, and for the next three decades the teleprinter was the standard means by which deaf people in the United States made telephone calls. The machines were heavy, slow and expensive, and they were replaced in time by software, but they provided one of the first practical text systems available outside industry.

Electricity has to be used at the instant it is generated, and the same is largely true of the heat produced in power stations. Yet demand for both rises and falls through the day, and much of the heat that industry needs could be produced when electricity is plentiful. Thermal energy storage is the name given to a group of technologies that hold heat — or, in some cases, cold — until it is wanted. The materials involved are usually ordinary: water, rock, sand, salts and waxes. That ordinariness is what makes the field interesting, because capacity can be scaled up with cheap substances rather than scarce metals.

The simplest method is to warm a material and keep it insulated; engineers call this sensible heat storage. The energy held depends on the mass of the material, its specific heat capacity and the difference between its starting and finishing temperatures. Water is excellent for the purpose, since it holds more heat per kilogram than almost any other common liquid, while concrete, bricks and crushed rock are preferred at higher temperatures. A tank of water or a pile of stone costs a small fraction of what a lithium-ion battery of the same capacity would cost, and can be built with ordinary materials.

Concentrated solar power stations have made the technology familiar. In these plants, mirrors focus sunlight to heat a fluid, which then drives a turbine. Because the sun sets, the earliest such plants could generate only in daylight; adding storage changed that. The first of the Andasol plants in southern Spain, which began operating in 2008, stores heat in two tanks of molten salt, and keeps generating for about seven and a half hours after sunset. A smaller plant near Seville, Gemasolar, which opened in 2011, holds enough for roughly fifteen hours. The salt, a mixture of sodium and potassium nitrates, must be kept above about 220°C or it solidifies and blocks the pipes.

A second family of materials stores heat without changing temperature very much. When a solid melts, it absorbs a quantity of energy known as latent heat, and it releases that energy again as it freezes. This allows a store to be compact and to deliver heat at a steady temperature, which suits buildings. Ice produced at night, when demand on the grid is low, can cool an office block through the following afternoon, and tanks of ice slurry are used in shopping centres and airports. Paraffin waxes and salt hydrates work in the same way, though many degrade after repeated cycles.

The least mature approach is thermochemical storage, in which heat drives a reversible chemical reaction. A salt is heated until it gives off water vapour; when water is added back later, the salt reabsorbs it and releases heat. Because the two products can be kept apart at room temperature, almost nothing is lost, and the energy density can be several times that of a tank of hot water. The obstacles are cost, complexity and the tendency of the materials to lose capacity after a limited number of cycles, which is why the technique remains confined to laboratories and small pilot plants.

One of the most striking demonstrations has nothing chemical about it. In 2022 a small company in Finland began operating a store consisting of a steel silo filled with about a hundred tonnes of sand. Electricity from the grid passes through heating elements buried in the sand and raises it to several hundred degrees. Air is then blown through pipes in the pile and carries heat to the local district heating network, which supplies homes and offices. Sand is cheap, does not freeze and can be heated far beyond the boiling point of water.

Thermal stores have an important limitation. Insulation is never perfect, so heat leaks away, slowly in a well-built tank but steadily over months. Converting stored heat back into electricity through a turbine discards a large share of it, so that perhaps a third of the original energy is recovered. This is why thermal storage is most convincing where heat itself is the product. Heat used directly for washing, drying or warming a building keeps most of its value, whereas heat turned back into electricity must compete with batteries that lose very little.

Industry may prove the largest market. Making cement, steel, glass and ceramics requires temperatures of several hundred to more than a thousand degrees, and most of that heat currently comes from burning gas or coal. Electric furnaces can supply it, but only when the grid has spare capacity or prices are low, which makes storage valuable. Researchers are testing stacks of refractory bricks and graphite blocks that electric elements can heat to well over a thousand degrees before giving up their heat to a stream of gas. The main difficulty is not the principle but the engineering: pumps, valves and bricks must survive years of cycling.

Governments have begun to treat the field as strategic. Because a thermal store can be built almost anywhere from locally available materials, it offers a way to shift large amounts of energy without depending on imported lithium or cobalt. Computer models now let designers test how a store will behave across a year, and engineers have buried insulated pits holding thousands of cubic metres of water, charged by solar collectors in summer and drawn on in winter. Seasonal storage on this scale remains expensive, but it addresses a problem that batteries cannot solve at any plausible cost.

The phrase 'digital nomad' was coined in 1997 by the engineer Tsugio Makimoto and the journalist David Manners, who predicted that mobile computing would allow people to live and work wherever they chose. For more than a decade the idea remained a curiosity, confined to a few freelancers with laptops. Then, from about 2014, cheap co-working spaces, reliable mobile data and cloud software turned it into an identifiable way of life, and a small industry of blogs, conferences and tax advisers grew up around it. The pandemic accelerated the change by normalising remote work for millions of office employees who had never expected to work from home, let alone from another country.

Measuring the phenomenon is difficult, and most of the numbers quoted are unreliable. Definitions differ: does a software developer who spends two months a year in another country count, or only someone with no fixed address at all? Self-selected online surveys attract people who are enthusiastic about the lifestyle, and they are often run by companies selling services to that same group. Governments rarely keep records, and visa statistics capture only those who apply for a dedicated permit. The honest conclusion is that nobody knows how many digital nomads there are, although all the available evidence suggests that the number is small in relation to the workforce as a whole.

What attracts people is easy to understand. A salary earned in a strong currency goes much further in a country with lower living costs, and the removal of the daily commute gives back hours that were previously lost. Nomads describe the freedom to choose a climate, to learn a language by living in it and to spend a winter somewhere warm while continuing to earn. There is an economic logic beneath the romance: wages are set by the market in which a person sells their labour, while rents and groceries are set by the place where they live, and the gap between the two is the nomad's real income.

The difficulties are less often advertised. Visas come first: tourist permits usually forbid paid work, and a growing number of countries have created special permits that allow it for a year or so, often on condition that the applicant earns a certain income or holds health insurance. Healthcare is a second problem, since travel insurance is not designed to cover a long illness and local health systems may exclude newcomers. The third is professional: work that depends on colleagues in another time zone, on a stable internet connection or on a legal right to be in a particular country is not really mobile at all, whatever the photographs suggest.

Cities that become popular with remote workers have discovered the costs. In Lisbon, Medellín, Mexico City and parts of Bali, the arrival of relatively wealthy visitors with foreign incomes has been blamed for rises in rents that fall hardest on local tenants, and for the conversion of residential streets into short-term lets and cafés catering to laptops. The effect is not unique to nomads — mass tourism does something similar — but it is sharpened when the newcomers stay for months and behave like residents without carrying the obligations of residents.

The most important issue, however, is one that few of the participants discuss. Income tax, social insurance and employment law all assume that a worker is ordinarily in one place. When an employee moves between countries, it is unclear where the tax on their salary should be paid, and a company may create a taxable presence in a country simply by allowing a member of staff to work there for long enough. Most nomads are freelancers who are supposed to declare their income somewhere; in practice, many spend less than the period that would make them resident anywhere.

None of this would matter much if the lifestyle were as widespread as its coverage implies. It is not. The great majority of jobs cannot be done from a beach: they involve physical equipment, face-to-face care or machinery that must be in a particular place. Even among the jobs that could in principle be performed anywhere, most people who work remotely do so from a home a short distance from their employer, not from another continent. Digital nomadism is a small elite practice that has attracted a great deal of attention because it is photogenic.

What, then, should we make of it? I would argue that the nomad is less a new kind of worker than a symptom of rules designed for a settled world. The sensible response is neither to romanticise the lifestyle nor to blame it for every rent rise, but to make the rules fit: define when a mobile worker becomes a taxpayer of the country they are living in, and require employers to register where their staff actually are. Cities should welcome the value that visitors bring and may reasonably charge them for it, but they should not build housing policy or public finances on the assumption that they will keep coming. The world of work has become mobile; the institutions that govern it have not.