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In Britain such systems were used for a time in areas where reception from conventional BBC radio transmitters was poor. In these systems programs were fed by special transformers into the lines. To prevent uncontrolled propagation, filters for the service's carrier frequencies were installed in substations and at line branches.
A variant of the 1950s L-3 system was designed in the early 1960s to provide for land line connections between key military command and control facilities in the United States. Starting with L-3I (improved) the system was upgraded to be able to withstand nuclear attack. The system consisted of over 100 main stations and 1000 individual repeater ...
These systems were replaced by cheaper and more versatile electrical systems, but by the end of the 19th century, city planners and financiers were well aware of the benefits, economics, and process of establishing power transmission systems. In the early days of electric power usage, widespread transmission of electric power had two obstacles ...
The pair of wires from the central office switch to a subscriber's home is called a subscriber loop. It carries a direct current (DC) voltage at a nominal voltage of −48V when the receiver is on-hook, supplied by a power conversion system in the central office. This power conversion system is backed up with a bank of batteries, resulting in ...
Long-distance open-wire pole line along Amsterdam Avenue in New York City. (Abbott, 1903) [1] Open wire was an early transmission technology in telecommunication, first used in telegraphy. It consisted of pairs of electric wire strung on a pole line between communities, towns, and cities. AT&T pin-type glass insulator for long-distance ...
HBO was the first true premium cable (or "pay-cable") network as well as the first television network intended for cable distribution on a regional or national basis; however, there were notable precursors to premium cable in the pay-television industry that operated during the 1950s and 1960s (with a few systems lingering until 1980), as well ...
The Alaska Communication System (ACS), also known as the Washington-Alaska Military Cable and Telegraph System (WAMCATS), was a system of cables and telegraph lines authorized by the U.S. Congress in 1900 and constructed by the U.S. Army Signal Corps. The communications lines were to serve both military and civilian needs in the territory of ...
At the outset, cable systems only served smaller communities without television stations of their own, and which could not easily receive signals from stations in cities because of distance or hilly terrain. In Canada, however, communities with their own signals were fertile cable markets, as viewers wanted to receive American signals.