Microducts are small ducts for the installation of small microduct fibre optic cables. They have a size ranging from 3 to 16 mm and are installed as bundles in larger ducts. Microducts are small-diameter, flexible, or semi-flexible ducts designed to provide clean, low-friction paths for placing optical cables that have low pulling tension limits; as stated in industry requirements document Telcordia GR-3155, Generic Requirements for Microducts for Fiber Optic Cables, microduct products are expected to: Be compatible with existing construction designs and building configurations for both riser- and plenum-rated applications, including cable blowing apparatus. Allow cables to be safely deployed through pull lines or strings using less than 50 lbs of force, through cable blowing techniques at typical deployment speeds of 100-200 feet per minute. GR-3155 states that the basic types of duct are smoothwall and ribbed; the selection of a particular duct design is dependent on those characteristics that are important to the end-user.
The need for a specific characteristic or combination of characteristics such as pulling strength, flexibility, or the lowest coefficient of friction will dictate the type of duct required. Ducts can be purchased with a variety of features. One such enhancement is pre-lubrication. Pre-lubricated ducts may be either permanently impregnated with anti-friction compounds or coated with liquid lubricant during manufacture; this may or may not eliminate the need for supplementary lubrication when pulling cable into the duct. Before using a supplementary lubricant with a pre-lubricated duct, the user should check with the manufacturer to determine if the added lubricant is compatible with the pre-lubricated surface of the duct. Failure to do this may result in the cable seizing up rather than reducing the friction coefficient of the duct; as indicated in GR-3155, cable is placed into the duct in one of three ways: It may be pre-installed by the duct manufacturer during the extrusion process. It may be pulled into the duct using a hand-drawn pull line.
It may be blown into the duct using a high air volume cable blowing apparatus. When cable is pre-installed, the duct manufacturer extrudes the duct directly over the optical cable. Tight control of the duct temperature during the manufacturing process is essential to ensure that the duct does not stick to the cable as it cools. At the completion of the process, all of the fibers in the optical cable must be tested to ensure that no damage has occurred. A common cable installation technique for fiber cables remains cable pulling. After the duct is placed, a high-strength pull line is blown into the duct; the pull line is used to pull the cable through the duct. Traditional cable pulling methods are sensitive to the condition of the duct and to the number of bends and undulations throughout the duct route. Therefore, for microducts, Air-Blown cable installation techniques are expected to be the most useful. AB cable installation requires the use of a device that injects a high volume of air into the duct, at pressures as high as 20-25 psi.
The viscous drag forces generated by the rushing air along the length of the cable act to reduce or overcome the friction between the cable and the duct. For telecommunications, cables can be installed in air or underground. In the latter case, the cables might be direct installed in ducts; the first is more common for copper balanced cables. The ducts in which the fibre optic cables are installed are made of polyethylene, they have a size ranging from 25 mm to 100 mm. Sometimes they are installed as subducts in larger ducts; these larger ducts can consist of other materials, like concrete. The installation of fibre optic cables in ducts can be done by cable jetting, it is more difficult to make branching fibre optic networks in the access network than it is for copper balanced cables. Splicing optical fibres is much more difficult than connecting copper wires. In Fibre to the Home, where a lot of branches are present in the network, an Optical Distribution Network is used to branch the cables from a roadside cabinet or pit that contains optical equipment and is fed from the Central Office With microduct cabling, bundles of small microducts are installed in larger protective ducts.
This can be done by jetting for example. Bundles of microducts can be factory pre-installed; the microducts can be branched easily in the network. At any place of choice, a window cut is made in the protective duct and the microduct of choice is cut; this microduct is connected, using a simple push/pull connector, to a microduct that branches to the desired location. After all connections are made, an individual microduct path has been created in the network. A microduct cable can be jetted through the microduct, without the need to make a splice. A branch can be made any place, at any time. Low initial costs; the network can grow on demand. Easy to install microduct routes in occupied ducts. Easy to replace old cables through the network. Possibility to migrate from copper balanced cables to fibre optic cables. Today the microduct cabling technology is used more, all over the world; the fibre counts have grown up to 96 per cable and can be installed in microducts of only 8 mm inner diameter. Bundles of microducts can be jetted over 1500 m or more.
Microduct cables can be jetted over 3.5 km in one single shot. More length without splice is reached by placing jetting equipment in tandem. Griffioen, W. "Installation of optical cables in
An electrical conduit is a tube used to protect and route electrical wiring in a building or structure. Electrical conduit may be made of metal, fiber, or fired clay. Most conduit is rigid. Conduit is installed by electricians at the site of installation of electrical equipment, its use and installation details are specified by wiring regulations, such as the US National Electrical Code and other building codes. Some early electric lighting installations made use of existing gas pipe serving gas light fixtures, converted to electric lamps. Since this technique provided good mechanical protection for interior wiring, it was extended to all types of interior wiring and by the early 20th century purpose-built couplings and fittings were manufactured for electrical use. However, most electrical codes now prohibit the routing of electrical conductors through gas piping, due to concerns about damage to electrical insulation from the rough interiors of pipes and fittings used for gas. Electrical conduit provides good protection to enclosed conductors from impact and chemical vapors.
Varying numbers and types of conductors can be pulled into a conduit, which simplifies design and construction compared to multiple runs of cables or the expense of customized composite cable. Wiring systems in buildings may be subject to frequent alterations. Frequent wiring changes are made simpler and safer through the use of electrical conduit, as existing conductors can be withdrawn and new conductors installed, with little disruption along the path of the conduit. A conduit system can be made submersible. Metal conduit can be used to shield sensitive circuits from electromagnetic interference, can prevent emission of such interference from enclosed power cables. Non-metallic conduits are light-weight, reducing installation labor cost; when installed with proper sealing fittings, a conduit will not permit the flow of flammable gases and vapors, which provides protection from fire and explosion hazard in areas handling volatile substances. Some types of conduit are approved for direct encasement in concrete.
This is used in commercial buildings to allow electrical and communication outlets to be installed in the middle of large open areas. For example, retail display cases and open-office areas use floor-mounted conduit boxes to connect power and communications cables. Both metal and plastic conduit can be bent at the job site to allow a neat installation without excessive numbers of manufactured fittings; this is advantageous when following irregular or curved building profiles. Special tube bending equipment is used to bend the conduit without denting it; the cost of conduit installation is higher than other wiring methods due to the cost of materials and labor. In applications such as residential construction, the high degree of physical damage protection may not be required, so the expense of conduit is not warranted. Conductors installed within conduit cannot dissipate heat as as those installed in open wiring, so the current capacity of each conductor must be reduced if many are installed in one conduit.
It is impractical, prohibited by wiring regulations, to have more than 360 degrees of total bends in a run of conduit, so special outlet fittings must be provided to allow conductors to be installed without damage in such runs. Some types of metal conduit may serve as a useful bonding conductor for grounding, but wiring regulations may dictate workmanship standards or supplemental means of grounding for certain types. While metal conduit may sometimes be used as a grounding conductor, the circuit length is limited. For example, a long run of conduit as grounding conductor may have too high an electrical resistance, not allow proper operation of overcurrent devices on a fault. Conduit systems are classified by the wall thickness, mechanical stiffness, material used to make the tubing. Materials may be chosen for mechanical protection, corrosion resistance, overall cost of the installation. Wiring regulations for electrical equipment in hazardous areas may require particular types of conduit to be used to provide an approved installation.
Rigid metal conduit is a thick-walled threaded tubing made of coated steel, stainless steel or aluminum. Galvanized rigid conduit is galvanized steel tubing, with a tubing wall, thick enough to allow it to be threaded, its common applications are in industrial construction. Intermediate metal conduit is a steel tubing heavier than EMT but lighter than RMC, it may be threaded. Electrical metallic tubing, sometimes called thin-wall, is used instead of galvanized rigid conduit, as it is less costly and lighter than GRC. EMT itself can be used with threaded fittings that clamp to it. Lengths of conduit are connected to equipment with clamp-type fittings. Like GRC, EMT is more common in commercial and industrial buildings than in residential applications. EMT is made of coated steel, though it may be aluminum. Aluminum conduit, similar to galvanized steel conduit, is a rigid tube used in commercial and industrial applications where a higher resistance to corrosion is needed; such locations would include food processing plants, where large amounts of water and cleaning chemicals would make galvanized conduit unsuitable.
Aluminum can not be directly embedded in concrete. The conduit may be coated to prevent corrosion by incidental contact with concrete. Aluminum conduit is lower cost than steel in
Telecommunication is the transmission of signs, messages, writings and sounds or information of any nature by wire, optical or other electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology, it is transmitted either electrically over physical media, such as cables, or via electromagnetic radiation. Such transmission paths are divided into communication channels which afford the advantages of multiplexing. Since the Latin term communicatio is considered the social process of information exchange, the term telecommunications is used in its plural form because it involves many different technologies. Early means of communicating over a distance included visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, optical heliographs. Other examples of pre-modern long-distance communication included audio messages such as coded drumbeats, lung-blown horns, loud whistles. 20th- and 21st-century technologies for long-distance communication involve electrical and electromagnetic technologies, such as telegraph and teleprinter, radio, microwave transmission, fiber optics, communications satellites.
A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909, other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included Charles Wheatstone and Samuel Morse, Alexander Graham Bell, Edwin Armstrong and Lee de Forest, as well as Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth; the word telecommunication is a compound of the Greek prefix tele, meaning distant, far off, or afar, the Latin communicare, meaning to share. Its modern use is adapted from the French, because its written use was recorded in 1904 by the French engineer and novelist Édouard Estaunié. Communication was first used as an English word in the late 14th century, it comes from Old French comunicacion, from Latin communicationem, noun of action from past participle stem of communicare "to share, divide out.
Homing pigeons have been used throughout history by different cultures. Pigeon post had Persian roots, was used by the Romans to aid their military. Frontinus said; the Greeks conveyed the names of the victors at the Olympic Games to various cities using homing pigeons. In the early 19th century, the Dutch government used the system in Sumatra, and in 1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels, a service that operated for a year until the gap in the telegraph link was closed. In the Middle Ages, chains of beacons were used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use was during the Spanish Armada, when a beacon chain relayed a signal from Plymouth to London. In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system between Lille and Paris.
However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres. As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880. On 25 July 1837 the first commercial electrical telegraph was demonstrated by English inventor Sir William Fothergill Cooke, English scientist Sir Charles Wheatstone. Both inventors viewed their device as "an improvement to the electromagnetic telegraph" not as a new device. Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837, his code was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable was completed on 27 July 1866, allowing transatlantic telecommunication for the first time; the conventional telephone was invented independently by Alexander Bell and Elisha Gray in 1876. Antonio Meucci invented the first device that allowed the electrical transmission of voice over a line in 1849.
However Meucci's device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to "hear" what was being said. The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London. Starting in 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using the newly discovered phenomenon of radio waves, showing by 1901 that they could be transmitted across the Atlantic Ocean; this was the start of wireless telegraphy by radio. Voice and music had little early success. World War I accelerated the development of radio for military communications. After the war, commercial radio AM broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated development of radio for the wartime purposes of aircraft and land communication, radio navigation and radar. Development of stereo FM broadcasting of radio
An optical fiber is a flexible, transparent fiber made by drawing glass or plastic to a diameter thicker than that of a human hair. Optical fibers are used most as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths than electrical cables. Fibers are used instead of metal wires. Fibers are used for illumination and imaging, are wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are used for a variety of other applications, some of them being fiber optic sensors and fiber lasers. Optical fibers include a core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total internal reflection which causes the fiber to act as a waveguide. Fibers that support many propagation paths or transverse modes are called multi-mode fibers, while those that support a single mode are called single-mode fibers.
Multi-mode fibers have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,000 meters. Being able to join optical fibers with low loss is important in fiber optic communication; this is more complex than joining electrical wire or cable and involves careful cleaving of the fibers, precise alignment of the fiber cores, the coupling of these aligned cores. For applications that demand a permanent connection a fusion splice is common. In this technique, an electric arc is used to melt the ends of the fibers together. Another common technique is a mechanical splice, where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors; the field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics.
The term was coined by Indian physicist Narinder Singh Kapany, acknowledged as the father of fiber optics. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon and Jacques Babinet in Paris in the early 1840s. John Tyndall included a demonstration of it in his public lectures in London, 12 years later. Tyndall wrote about the property of total internal reflection in an introductory book about the nature of light in 1870:When the light passes from air into water, the refracted ray is bent towards the perpendicular... When the ray passes from water to air it is bent from the perpendicular... If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the ray will not quit the water at all: it will be reflected at the surface.... The angle which marks the limit where total reflection begins is called the limiting angle of the medium. For water this angle is 48°27′, for flint glass it is 38°41′, while for diamond it is 23°42′.
In the late 19th and early 20th centuries, light was guided through bent glass rods to illuminate body cavities. Practical applications such as close internal illumination during dentistry appeared early in the twentieth century. Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. In the 1930s, Heinrich Lamm showed that one could transmit images through a bundle of unclad optical fibers and used it for internal medical examinations, but his work was forgotten. In 1953, Dutch scientist Bram van Heel first demonstrated image transmission through bundles of optical fibers with a transparent cladding; that same year, Harold Hopkins and Narinder Singh Kapany at Imperial College in London succeeded in making image-transmitting bundles with over 10,000 fibers, subsequently achieved image transmission through a 75 cm long bundle which combined several thousand fibers. Their article titled "A flexible fibrescope, using static scanning" was published in the journal Nature in 1954.
The first practical fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz, C. Wilbur Peters, Lawrence E. Curtiss, researchers at the University of Michigan, in 1956. In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers. A variety of other image transmission applications soon followed. Kapany coined the term fiber optics, wrote a 1960 article in Scientific American that introduced the topic to a wide audience, wrote the first book about the new field; the first working fiber-optical data transmission system was demonstrated by German physicist Manfred Börner at Telefunken Research Labs in Ulm in 1965, followed by the first patent application for this technology in 1966. NASA used fiber optics in the television cameras. At the time, the use in the cameras was classified confidential, employees handling the cameras had to be supervised by someone with an appropriate security clearance. Charles K. Kao and George A. Hockham of the British company Standard Telephones and Cables were the first, in 1965, to promote the idea that the attenuation in optical fibers could be reduced below 20 decibels per kilometer, making fibers a practical communication medium.
They proposed th
A metamaterial is a material engineered to have a property, not found in occurring materials. They are made from assemblies of multiple elements fashioned from composite materials such as metals or plastics; the materials are arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence. Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures, their precise shape, size and arrangement gives them their smart properties capable of manipulating electromagnetic waves: by blocking, enhancing, or bending waves, to achieve benefits that go beyond what is possible with conventional materials. Appropriately designed metamaterials can affect waves of electromagnetic radiation or sound in a manner not observed in bulk materials; those that exhibit a negative index of refraction for particular wavelengths have attracted significant research. These materials are known as negative-index metamaterials.
Potential applications of metamaterials are diverse and include optical filters, medical devices, remote aerospace applications, sensor detection and infrastructure monitoring, smart solar power management, crowd control, high-frequency battlefield communication and lenses for high-gain antennas, improving ultrasonic sensors, shielding structures from earthquakes. Metamaterials offer the potential to create superlenses; such a lens could allow imaging below the diffraction limit, the minimum resolution that can be achieved by conventional glass lenses. A form of'invisibility' was demonstrated using gradient-index materials. Acoustic and seismic metamaterials are research areas. Metamaterial research is interdisciplinary and involves such fields as electrical engineering, classical optics, solid state physics and antenna engineering, material sciences and semiconductor engineering. Explorations of artificial materials for manipulating electromagnetic waves began at the end of the 19th century.
Some of the earliest structures that may be considered metamaterials were studied by Jagadish Chandra Bose, who in 1898 researched substances with chiral properties. Karl Ferdinand Lindman studied wave interaction with metallic helices as artificial chiral media in the early twentieth century. Winston E. Kock developed materials that had similar characteristics to metamaterials in the late 1940s. In the 1950s and 1960s, artificial dielectrics were studied for lightweight microwave antennas. Microwave radar absorbers were researched in the 1980s and 1990s as applications for artificial chiral media. Negative-index materials were first described theoretically by Victor Veselago in 1967, he proved. He showed; this is contrary to wave propagation in occurring materials. John Pendry was the first to identify a practical way to make a left-handed metamaterial, a material in which the right-hand rule is not followed; such a material allows an electromagnetic wave to convey energy against its phase velocity.
Pendry's idea was that metallic wires aligned along the direction of a wave could provide negative permittivity. Natural materials display negative permittivity. In 1999 Pendry demonstrated that a split ring with its axis placed along the direction of wave propagation could do so. In the same paper, he showed that a periodic array of wires and rings could give rise to a negative refractive index. Pendry proposed a related negative-permeability design, the Swiss roll. In 2000, Smith et al. reported the experimental demonstration of functioning electromagnetic metamaterials by horizontally stacking, split-ring resonators and thin wire structures. A method was provided in 2002 to realize negative-index metamaterials using artificial lumped-element loaded transmission lines in microstrip technology. In 2003, complex negative refractive index and imaging by flat lens using left handed metamaterials were demonstrated. By 2007, experiments that involved negative refractive index had been conducted by many groups.
At microwave frequencies, the first, imperfect invisibility cloak was realized in 2006. An electromagnetic metamaterial affects electromagnetic waves that impinge on or interact with its structural features, which are smaller than the wavelength. To behave as a homogeneous material described by an effective refractive index, its features must be much smaller than the wavelength. For microwave radiation, the features are on the order of millimeters. Microwave frequency metamaterials are constructed as arrays of electrically conductive elements that have suitable inductive and capacitive characteristics. One microwave metamaterial uses the split-ring resonator. Photonic metamaterials, nanometer scale, manipulate light at optical frequencies. To date, subwavelength structures have shown only a few, results at visible wavelengths. Photonic crystals and frequency-selective surfaces such as diffraction gratings, dielectric mirrors and optical coatings exhibit similarities to subwavelength structured metamaterials.
However, these are considered distinct from subwavelength structures, as their features are structured for the wavelength at which they function and thus cannot be approximated as a homogeneous material. However, material structures such as photonic crystals are effective in the visible light spectrum; the m
A dark fibre or unlit fibre is an unused optical fibre, available for use in fibre-optic communication. Dark fibre referred to the potential network capacity of telecommunication infrastructure. Dark fibre may be leased from a network service provider. Much of the cost of installing cables is in the civil engineering work required; this includes planning and routing, obtaining permissions, creating ducts and channels for the cables, installation and connection. This work accounts for most of the cost of developing fibre networks. For example, in Amsterdam's citywide installation of a fibre network 80% of the costs involved were labour, with only 10% being fibre, it therefore makes sense to plan for, install more fibre than is needed for current demand, to provide for future expansion and provide for network redundancy in case any of the cables fail. Many fibre optic cable owners such as railroads and power utilities have always included additional fibres with the intention to lease these to other carriers.
During the dot-com bubble, a large number of telephone companies built optical fibre networks, each with the business plan of cornering the market in telecommunications by providing a network with sufficient capacity to take all existing and forecast traffic for the entire region served. This was based on the assumption that telecoms traffic data traffic, would continue to grow exponentially for the foreseeable future; the availability of wavelength-division multiplexing reduced the demand for fibre by increasing the capacity that could be placed on a single fibre by a factor of as much as 100. As a result, the wholesale price of data traffic collapsed. A number of these companies filed for bankruptcy protection as a result. Global Crossing and Worldcom are two high-profile examples in the US. According to Gerry Butters, the former head of Lucent's Optical Networking Group at Bell Labs, the amount of data that could be carried by an optical fibre was doubling every nine months at the time; this progress in the ability to carry data over fiber reduced the need for more fibres.
Just as with the Railway Mania, the misfortune of one market sector became the good fortune of another, this overcapacity created a new telecommunications market sector. For many years incumbent local exchange carriers would not sell dark fibre to end users, because they believed selling access to this core asset would cannibalize their other, more lucrative services. Incumbent carriers in the US were required to sell dark fibre to competitive local exchange carriers as unbundled network elements, but they have lobbied to reduce these provisions for existing fibre, eliminated it for new fibre placed for fibre to the premises deployments. Fibre swaps between competitive carriers are quite common; this increases the reach of their networks in places where their competitor has a presence, in exchange for the provision of fibre capacity in places where that competitor has no presence. This is a practice known in the industry as "coopetition". Meanwhile, other companies arose specializing as dark fibre providers.
Dark fibre became more available when there was enormous overcapacity after the telecoms boom years of the late 1990s through 2001. The market for dark fibre tightened up with the return of capital investment to light up existing fibre, with mergers and acquisitions resulting in a consolidation of dark fibre providers. In the last decade, many higher education institutions have bought up large quantities of existing fibre optics sitting dormant. Starting in 1999, Larry Smarr, a technology director from the University of Illinois, connected the Urbana-Champaign campus to major academic and telecommunications facilities in the Chicago area. At the same time, other schools began creating large urban networks to directly connect their school campuses with hospitals and large telecommunications companies in metropolitan areas. Since US research and education institutions have been aggressively pursuing a revolutionary new means for delivering advanced networking capabilities. With the plummeting prices of fibre due to the overabundance, the option to own fibre networks has reduced the competitive leasing of commercial circuits elsewhere.
Experts say that a mile of dark fibre that in the past would have sold for $1,200, has sold for as low $200 or less. The downturn in telecommunications has offered significant savings to schools, since intercity networks may include several hundred to several thousand miles of fibre optic cable. Dark fibre can be used to create a operated optical fiber network, run directly by its operator over dark fibre leased or purchased from another supplier; this is opposed to leased line capacity on an existing network. Dark fibre networks may be used for private networking, or as Internet access or Internet infrastructure networking. Dark fibre networks may use star self-healing ring or mesh topologies; because both ends of the link is controlled by the same organization, dark fibre networks can operate using the latest optical protocols using wavelength division multiplexing to add capacity where needed, to provide an upgrade path between technologies. Many dark fibre metropolitan area networks use cheap Gigabit Ethernet equipment over CWDM, rather than expensive SONET ring systems.
They offer high price-performance for network users who require high performance, such as Google, which has dark network capacities for video and search data, or wish to operate their own network for security or other commercial reasons. However, dark fibre networks are only available in high-population-density areas where fibre has been laid, as the civil engineering costs of installin
Empire City Subway
Empire City Subway is an American company in New York City, responsible for maintaining underground conduits in Manhattan and The Bronx, the manholes by which those conduits are accessed. The company was formed in 1891 as part of a plan for common utility ducts to consolidate all utilities underground. Incompatibility among the utilities limited the range of utilities that could share their ducts, so the company now operates as a wholly owned subsidiary of Verizon New York Telephone under a franchise from the city. In addition to Verizon, the company provides service to cable television and other telephone companies. Manholes owned by Empire City Subway can be recognized by the abbreviation ECS cast into the metal covers. List of companies based in New York City empirecitysubway.com/home.html, the company's official website