General Services Administration
The General Services Administration, an independent agency of the United States government, was established in 1949 to help manage and support the basic functioning of federal agencies. GSA supplies products and communications for U. S. government offices, provides transportation and office space to federal employees, develops government-wide cost-minimizing policies and other management tasks. GSA employs about 12,000 federal workers and has an annual operating budget of $20.9 billion. GSA oversees $66 billion of procurement annually, it contributes to the management of about $500 billion in U. S. federal property, divided chiefly among 8,700 owned and leased buildings and a 215,000 vehicle motor pool. Among the real estate assets managed by GSA are the Ronald Reagan Building and International Trade Center in Washington, D. C. – the largest U. S. federal building after the Pentagon – and the Hart-Dole-Inouye Federal Center. GSA's business lines include the Federal Acquisition Service and the Public Buildings Service, as well as several Staff Offices including the Office of Government-wide Policy, the Office of Small Business Utilization, the Office of Mission Assurance.
As part of FAS, GSA's Technology Transformation Services helps federal agencies improve delivery of information and services to the public. Key initiatives include FedRAMP, Cloud.gov, the USAGov platform, Data.gov, Performance.gov, Challenge.gov. GSA is a member of the Procurement G6, an informal group leading the use of framework agreements and e-procurement instruments in public procurement. In 1947 President Harry Truman asked former President Herbert Hoover to lead what became known as the Hoover Commission to make recommendations to reorganize the operations of the federal government. One of the recommendations of the commission was the establishment of an "Office of the General Services." This proposed office would combine the responsibilities of the following organizations: U. S. Treasury Department's Bureau of Federal Supply U. S. Treasury Department's Office of Contract Settlement National Archives Establishment All functions of the Federal Works Agency, including the Public Buildings Administration and the Public Roads Administration War Assets AdministrationGSA became an independent agency on July 1, 1949, after the passage of the Federal Property and Administrative Services Act.
General Jess Larson, Administrator of the War Assets Administration, was named GSA's first Administrator. The first job awaiting Administrator Larson and the newly formed GSA was a complete renovation of the White House; the structure had fallen into such a state of disrepair by 1949 that one inspector of the time said the historic structure was standing "purely from habit." Larson explained the nature of the total renovation in depth by saying, "In order to make the White House structurally sound, it was necessary to dismantle, I mean dismantle, everything from the White House except the four walls, which were constructed of stone. Everything, except the four walls without a roof, was stripped down, that's where the work started." GSA worked with President Truman and First Lady Bess Truman to ensure that the new agency's first major project would be a success. GSA completed the renovation in 1952. In 1986 GSA headquarters, U. S. General Services Administration Building, located at Eighteenth and F Streets, NW, was listed on the National Register of Historic Places, at the time serving as Interior Department offices.
In 1960 GSA created the Federal Telecommunications System, a government-wide intercity telephone system. In 1962 the Ad Hoc Committee on Federal Office Space created a new building program to address obsolete office buildings in Washington, D. C. resulting in the construction of many of the offices that now line Independence Avenue. In 1970 the Nixon administration created the Consumer Product Information Coordinating Center, now part of USAGov. In 1974 the Federal Buildings Fund was initiated, allowing GSA to issue rent bills to federal agencies. In 1972 GSA established the Automated Data and Telecommunications Service, which became the Office of Information Resources Management. In 1973 GSA created the Office of Federal Management Policy. GSA's Office of Acquisition Policy centralized procurement policy in 1978. GSA was responsible for emergency preparedness and stockpiling strategic materials to be used in wartime until these functions were transferred to the newly-created Federal Emergency Management Agency in 1979.
In 1984 GSA introduced the federal government to the use of charge cards, known as the GMA SmartPay system. The National Archives and Records Administration was spun off into an independent agency in 1985; the same year, GSA began to provide governmentwide policy oversight and guidance for federal real property management as a result of an Executive Order signed by President Ronald Reagan. In 2003 the Federal Protective Service was moved to the Department of Homeland Security. In 2005 GSA reorganized to merge the Federal Supply Service and Federal Technology Service business lines into the Federal Acquisition Service. On April 3, 2009, President Barack Obama nominated Martha N. Johnson to serve as GSA Administrator. After a nine-month delay, the United States Senate confirmed her nomination on February 4, 2010. On April 2, 2012, Johnson resigned in the wake of a management-deficiency report that detailed improper payments for a 2010 "Western Regions" training conference put on by the Public Buildings Service in Las Vegas.
In July 1991 GSA contractors began the excavation of what is now the Ted Weiss Federal Building in New York City. The planning for that buildin
A loitering munition is a weapon system category in which the munition loiters around the target area for some time, searches for targets, attacks once a target is located. Loitering munitions enable faster reaction times against concealed or hidden targets that emerge for short periods without placing high-value platforms close to the target area, allow more selective targeting as the actual attack mission can be aborted. Loitering munitions fit in the niche between cruise missiles and unmanned combat aerial vehicles sharing characteristics with both, they differ from cruise missiles in that they are designed to loiter for a long time around the target area, from UCAVs in that a loitering munition is intended to be expended in an attack and has a built-in warhead. Loitering weapons first emerged in the 1980s for use in the Suppression of Enemy Air Defenses role against surface-to-air missiles, were deployed for the SEAD role in a number of military forces in the 1990s. Starting in the 2000s, loitering weapons have been developed for additional roles ranging from long-range strikes and fire support down to tactical short range battlefield systems that fit in a backpack.
Loitering munitions have proliferated into use by at least 14 countries, with several different types in use as of 2017. The rising proliferation and the ability to use some systems as lethal autonomous weapons coupled with ethical concerns over such use have led to research and discussion by International humanitarian law scholars and activists. Loitering munitions were not referred to as such but rather as suicide UAVs or loitering missiles. Different sources point at different projects as originating the weapon category; the early 1980s initial Israeli Delilah variants or the failed US AGM-136 Tacit Rainbow program are mentioned by some sources. Alternatively, the late 1980s IAI Harpy, exported is considered by some as the first loitering munition system. Early projects did not use the "loitering munition" nomenclature which emerged at a much date, used existing terminology at the time. For instance the AGM-136 Tacit Rainbow was described as follows in a 1988 Air Force Magazine article: the Tacit Rainbow unmanned jet aircraft being developed by Northrop to loiter on high and swoop down on enemy radars could be called a UAV, a cruise missile, or a standoff weapon.
But it is most not an RPV. The response to the first generation of fixed installation surface-to-air missiles such as SA-2 and SA-3 was the development of the anti-radiation missile such as AGM-45 Shrike and other means to attack fixed SAM installations, as well as developing SEAD doctrines; the Soviet counter-response was the use of mobile SAMs such as SA-6 with intermittent use of radar. Thus, the SAM battery was only visible for a small period of time, during which it was a significant threat to high-value Wild Weasel fighters. In 1982 Operation Mole Cricket 19 various means including UAVs and air-launched Samson decoys were used over suspected SAM areas to saturate enemy SAMs and to bait them to activate their radar systems, which were attacked by anti-radiation missiles. In the 1980s, a number of programs, such as the IAI Harpy or the AGM-136 Tacit Rainbow, integrated anti-radiation sensors into a drone or missile air frames coupled with command and control and loitering capabilities; this allowed the attacking force to place cheap munitions in place over suspected SAM sites, to attack promptly the moment the SAM battery is visible.
This integrated the use of a drone as a baiting decoy with the attack role into one small and cheap platform in comparison to the alternative wild weasel jet fighter. Starting in the 2000s, loitering weapons have been developed for additional roles beyond the initial SEAD role ranging from long-range strikes and fire support down to tactical short-range battlefield use such as the AeroVironment Switchblade, deployed at the platoon level and fits in a backpack. A documented use of loitering munitions was in 2016 Nagorno-Karabakh clashes in which an IAI Harop was used against a bus functioning as a troop transport. Loitering munitions may be as simple as an unmanned aerial vehicle with attached explosives, sent on a potential kamikaze mission, may be constructed with off the shelf commercial quadcopters with strapped on explosives. Purpose built munitions are more elaborate in flight and control capabilities, warhead size and design, on-board sensors for locating targets; some loitering munitions use a human operator to locate targets whereas others, such as IAI Harop, can function autonomously searching and launching attacks without human intervention.
Some loitering munitions may return and be recovered by the operator if they are unused in an attack and have enough fuel. Other systems, such as Delilah or IAI Harop, don't have a recovery option and are self-destructed in mission aborts. Loitering munitions fit in unmanned combat aerial vehicles; the following table compares similar size-class cruise missiles, loitering munitions, UCAVS: Whereas some cruise missiles, such as the block IV Tomahawk, have the ability to loiter and have some sensory and remote control features, their primary mission is strike and not target acquisition. Cruise missiles, as their name implies, are optimized for long-range flight at constant speed both in terms of propulsion systems and wings or lifting body design, they are unable to loiter at slow fuel-efficient speeds which reduces potential loiter time when the miss
Missile guidance refers to a variety of methods of guiding a missile or a guided bomb to its intended target. The missile's target accuracy is a critical factor for its effectiveness. Guidance systems improve missile accuracy by improving its "Single Shot Kill Probability", part of combat survivability calculations associated with the salvo combat model; these guidance technologies can be divided up into a number of categories, with the broadest categories being "active," "passive" and "preset" guidance. Missiles and guided bombs use similar types of guidance system, the difference between the two being that missiles are powered by an onboard engine, whereas guided bombs rely on the speed and height of the launch aircraft for propulsion; the concept of missile guidance originated at least as early as World War I, with the idea of remotely guiding an airplane bomb onto a target. In World War II, guided missiles were first developed, as part of the German V-weapons program. Project Pigeon was American behaviorist B.
F. Skinner's attempt to develop a pigeon-guided missile; the first U. S. ballistic missile with a accurate inertial guidance system was the short-range Redstone. Guidance systems are divided into different categories according to whether they are designed to attack fixed or moving targets; the weapons can be divided into two broad categories: Go-Onto-Target and Go-Onto-Location-in-Space guidance systems. A GOT missile can target either a moving or fixed target, whereas a GOLIS weapon is limited to a stationary or near-stationary target; the trajectory that a missile takes while attacking a moving target is dependent upon the movement of the target. A moving target can be an immediate threat to the sender of the missile; the target needs to be eliminated in a timely fashion in order to preserve the integrity of the sender. In GOLIS systems, the problem is simpler because the target is not moving. In every Go-Onto-Target system there are three subsystems: Target tracker Missile tracker Guidance computerThe way these three subsystems are distributed between the missile and the launcher result in two different categories: Remote Control Guidance: The guidance computer is on the launcher.
The target tracker is placed on the launching platform. Homing Guidance: The guidance computers are in the missile and in the target tracker; these guidance systems need the use of radars and a radio or wired link between the control point and the missile. These systems include: Command guidance - The missile tracker is on the launching platform; these missiles are controlled by the launching platform that sends all control orders to the missile. The 2 variants areCommand to Line-Of-Sight Command Off Line-Of-Sight Line-Of-Sight Beam Riding Guidance - The target tracker is on board the missile; the missile has some orientation capability meant for flying inside the beam that the launching platform is using to illuminate the target. It can be manual or automatic; the CLOS system uses only the angular coordinates between the missile and the target to ensure the collision. The missile is made to be in the line of sight between the launcher and the target, any deviation of the missile from this line is corrected.
Since so many types of missile use this guidance system, they are subdivided into four groups: A particular type of command guidance and navigation where the missile is always commanded to lie on the line of sight between the tracking unit and the aircraft is known as command to line of sight or three-point guidance. That is, the missile is controlled to stay as close as possible on the LOS to the target after missile capture is used to transmit guidance signals from a ground controller to the missile. More if the beam acceleration is taken into account and added to the nominal acceleration generated by the beam-rider equations CLOS guidance results. Thus, the beam rider acceleration command is modified to include an extra term; the beam-riding performance described above can thus be improved by taking the beam motion into account. CLOS guidance is used in shortrange air defense and antitank systems. Both target tracking and missile tracking and control are performed manually; the operator watches the missile flight, uses a signaling system to command the missile back into the straight line between operator and target.
This is useful only for slower targets, where significant "lead" is not required. MCLOS is a subtype of command guided systems. In the case of glide bombs or missiles against ships or the supersonic Wasserfall against slow-moving B-17 Flying Fortress bombers this system worked, but as speeds increased MCLOS was rendered useless for most roles. Target tracking is automatic, while missile tracking and control is manual. Target tracking is manual, but missile tracking and control is automatic. Is similar to MCLOS but some automatic system positions the missile in the line of sight while the operator tracks the target. SACLOS has the advantage of allowing the missile to start in a position invisible to the user, as well as being easier to operate, it is the most common form of guidance against ground targets such as tanks and bunkers. Target tracking, missile tracking and control are automatic; this guidance system was one of the first to be used and still is in service in anti-aircraft missiles. In this system, the target tracker and the missile tracker can be oriented in different directions.
The guidance system ensures the interception of the target by the missile by locating both in space. This m
A telephone, or phone, is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. In 1876, Scottish emigrant Alexander Graham Bell was the first to be granted a United States patent for a device that produced intelligible replication of the human voice; this instrument was further developed by many others. The telephone was the first device in history that enabled people to talk directly with each other across large distances. Telephones became indispensable to businesses and households and are today some of the most used small appliances; the essential elements of a telephone are a microphone to speak into and an earphone which reproduces the voice in a distant location. In addition, most telephones contain a ringer to announce an incoming telephone call, a dial or keypad to enter a telephone number when initiating a call to another telephone.
The receiver and transmitter are built into a handset, held up to the ear and mouth during conversation. The dial may be located either on a base unit to which the handset is connected; the transmitter converts the sound waves to electrical signals which are sent through a telephone network to the receiving telephone, which converts the signals into audible sound in the receiver or sometimes a loudspeaker. Telephones are duplex devices; the first telephones were directly connected to each other from one customer's office or residence to another customer's location. Being impractical beyond just a few customers, these systems were replaced by manually operated centrally located switchboards; these exchanges were soon connected together forming an automated, worldwide public switched telephone network. For greater mobility, various radio systems were developed for transmission between mobile stations on ships and automobiles in the mid-20th century. Hand-held mobile phones were introduced for personal service starting in 1973.
In decades their analog cellular system evolved into digital networks with greater capability and lower cost. Convergence has given most modern cell phones capabilities far beyond simple voice conversation, they may be able to record spoken messages and receive text messages and display photographs or video, play music or games, surf the Internet, do road navigation or immerse the user in virtual reality. Since 1999, the trend for mobile phones is smartphones that integrate all mobile communication and computing needs. A traditional landline telephone system known as plain old telephone service carries both control and audio signals on the same twisted pair of insulated wires, the telephone line; the control and signaling equipment consists of three components, the ringer, the hookswitch, a dial. The ringer, or beeper, light or other device, alerts the user to incoming calls; the hookswitch signals to the central office that the user has picked up the handset to either answer a call or initiate a call.
A dial, if present, is used by the subscriber to transmit a telephone number to the central office when initiating a call. Until the 1960s dials used exclusively the rotary technology, replaced by dual-tone multi-frequency signaling with pushbutton telephones. A major expense of wire-line telephone service is the outside wire plant. Telephones transmit both the outgoing speech signals on a single pair of wires. A twisted pair line rejects electromagnetic interference and crosstalk better than a single wire or an untwisted pair; the strong outgoing speech signal from the microphone does not overpower the weaker incoming speaker signal with sidetone because a hybrid coil and other components compensate the imbalance. The junction box arrests lightning and adjusts the line's resistance to maximize the signal power for the line length. Telephones have similar adjustments for inside line lengths; the line voltages are negative compared to earth. Negative voltage attracts positive metal ions toward the wires.
The landline telephone contains a switchhook and an alerting device a ringer, that remains connected to the phone line whenever the phone is "on hook", other components which are connected when the phone is "off hook". The off-hook components include a transmitter, a receiver, other circuits for dialing and amplification. A calling party wishing to speak to another party will pick up the telephone's handset, thereby operating a lever which closes the switchhook, which powers the telephone by connecting the transmitter and related audio components to the line; the off-hook circuitry has a low resistance which causes a direct current, which comes down the line from the telephone exchange. The exchange detects this current, attaches a digit receiver circuit to the line, sends a dial tone to indicate readiness. On a modern push-button telephone, the caller presses the number keys to send the telephone number of the called party; the keys control a tone generator circuit. A rotary-dial telephone uses pulse
A telephone exchange is a telecommunications system used in the public switched telephone network or in large enterprises. An exchange consists of electronic components and in older systems human operators that interconnect telephone subscriber lines or virtual circuits of digital systems to establish telephone calls between subscribers. In historical perspective, telecommunication terms have been used with different semantics over time; the term telephone exchange is used synonymously with central office, a Bell System term. A central office is defined as a building used to house the inside plant equipment of several telephone exchanges, each serving a certain geographical area; such an area has been referred to as the exchange. Central office locations may be identified in North America as wire centers, designating a facility from which a telephone obtains dial tone. For business and billing purposes, telephony carriers define rate centers, which in larger cities may be clusters of central offices, to define specified geographical locations for determining distance measurements.
In the United States and Canada, the Bell System established in the 1940s a uniform system of identifying central offices with a three-digit central office code, used as a prefix to subscriber telephone numbers. All central offices within a larger region aggregated by state, were assigned a common numbering plan area code. With the development of international and transoceanic telephone trunks driven by direct customer dialing, similar efforts of systematic organization of the telephone networks occurred in many countries in the mid-20th century. For corporate or enterprise use, a private telephone exchange is referred to as a private branch exchange, when it has connections to the public switched telephone network. A PBX is installed in enterprise facilities collocated with large office spaces or within an organizational campus to serve the local private telephone system and any private leased line circuits. Smaller installations might deploy a PBX or key telephone system in the office of a receptionist.
In the era of the electrical telegraph, post offices, railway stations, the more important governmental centers, stock exchanges few nationally distributed newspapers, the largest internationally important corporations and wealthy individuals were the principal users of such telegraphs. Despite the fact that telephone devices existed before the invention of the telephone exchange, their success and economical operation would have been impossible on the same schema and structure of the contemporary telegraph, as prior to the invention of the telephone exchange switchboard, early telephones were hardwired to and communicated with only a single other telephone. A telephone exchange is a telephone system located at service centers responsible for a small geographic area that provided the switching or interconnection of two or more individual subscriber lines for calls made between them, rather than requiring direct lines between subscriber stations; this made it possible for subscribers to call each other at businesses, or public spaces.
These made telephony an available and comfortable communication tool for everyday use, it gave the impetus for the creation of a whole new industrial sector. As with the invention of the telephone itself, the honor of "first telephone exchange" has several claimants. One of the first to propose a telephone exchange was Hungarian Tivadar Puskás in 1877 while he was working for Thomas Edison; the first experimental telephone exchange was based on the ideas of Puskás, it was built by the Bell Telephone Company in Boston in 1877. The world's first state-administered telephone exchange opened on November 12, 1877 in Friedrichsberg close to Berlin under the direction of Heinrich von Stephan. George W. Coy designed and built the first commercial US telephone exchange which opened in New Haven, Connecticut in January, 1878; the switchboard was built from "carriage bolts, handles from teapot lids and bustle wire" and could handle two simultaneous conversations. Charles Glidden is credited with establishing an exchange in Lowell, MA. with 50 subscribers in 1878.
In Europe other early telephone exchanges were based in London and Manchester, both of which opened under Bell patents in 1879. Belgium had its first International Bell exchange a year later. In 1887 Puskás introduced the multiplex switchboard.. Exchanges consisted of one to several hundred plug boards staffed by switchboard operators; each operator sat in front of a vertical panel containing banks of ¼-inch tip-ring-sleeve jacks, each of, the local termination of a subscriber's telephone line. In front of the jack panel lay a horizontal panel containing two rows of patch cords, each pair connected to a cord circuit; when a calling party lifted the receiver, the local loop current lit a signal lamp near the jack. The operator responded by inserting the rear cord into the subscriber's jack and switched her headset into the circuit to ask, "Number, please?" For a local call, the operator inserted the front cord of the pair into the called party's local jack and started the ringing cycle. For a long distance call, she plugged into a trunk circuit to connect to another operator in another bank of boards or at a remote central office.
In 1918, the average time to complete the connection for a long-distance call was 15 minutes. Early manual switchboards required the operator to operate listening keys and ringing keys, but by the late 1910s and 1920s, advances in switchboard technology led to features which allowed the call to be automatic
An access network is a type of telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network; the access network may be further divided between feeder plant or distribution network, drop plant or edge network. An access network referred to as an outside plant, refers to the series of wires and equipment lying between a consumer/business telephone termination point and the local telephone exchange; the local exchange contains banks of automated switching equipment which direct a call or connection to the consumer. The access network is one of the oldest assets a telecoms operator would own. In 2007–2008 many telecommunication operators experienced increasing problems maintaining the quality of the records which describe the network. In 2006, according to an independent Yankee Group report, globally operators experience profit leakage in excess of $17 billion each year; the access network is perhaps the most valuable asset an operator owns, since this is what physically allows them to offer a service.
Access networks consist of pairs of copper wires, each traveling in a direct path between the exchange and the customer. In some instances, these wires may consist of aluminum, used in the 1960s and 1970s following a massive increase in the cost of copper; as it happened, the price increase was temporary, but the effects of this decision are still felt today as electromigration within the aluminum wires can cause an increase in on-state resistance. This resistance causes degradation which can lead to the complete failure of the wire to transport data. Access is essential to the future profitability of operators who are experiencing massive reductions in revenue from plain old telephone services, due in part to the opening of nationalized companies to competition, in part to increased use of mobile phones and voice over IP services. Operators offered additional services such as xDSL based IPTV to guarantee profit; the access network is again the main barrier to achieving these profits since operators worldwide have accurate records of only 40% to 60% of the network.
Without understanding or knowing the characteristics of these enormous copper spider webs, it is difficult, expensive to'provision' new customers and assure the data rates required to receive next generation services. Access networks around the world evolved to include more optical fiber technology. Optical fibre makes up the majority of core networks and will start to creep closer and closer to the customer, until a full transition is achieved, delivering value added services over fiber to the home; the process of communicating with a network begins with an access attempt, in which one or more users interact with a communications system to enable initiation of user information transfer. An access attempt. An access attempt ends either in successful access or in access failure - an unsuccessful access that results in termination of the attempt in any manner other than initiation of user information transfer between the intended source and destination within the specified maximum access time.
Access failure can be the result of access outage, user blocking, incorrect access, or access denial. Access denial can include: Access failure caused by the issuing of a system blocking signal by a communications system that does not have a camp-on busy signal feature. Access failure caused by exceeding the maximum access time and nominal system access time fraction during an access attempt. An access charge is a charge made by a local exchange carrier for use of its local exchange facilities for a purpose such as the origination or termination of network traffic, carried to or from a distant exchange by an interexchange carrier. Although some access charges are billed directly to interexchange carriers, a significant percentage of all access charges are paid by the local end users. GERAN UTRAN E-UTRAN CDMA2000 GSM UMTS 1xEVDO voLTE Wi-Fi in* WiMAX A passive optical distribution network uses single mode optical fibre in the outside plant, optical splitters and optical distribution frames, duplexed so that both upstream and downstream signals share the same fibre on separate wavelengths.
Faster PON standards support a higher split ratio of users per PON, but may use reach extenders/amplifiers where extra coverage is needed. Optical splitters creating a point to multipoint topology are the same technology regardless of the type of PON system, making any PON network upgradable by changing the optical network terminals and optical line terminal terminals at each end, with minimal change to the physical network. Access networks also must support point-to-point technologies such as Ethernet, which bypasses any outside plant splitter to achieve a dedicated link to the telephone exchange; some PON networks use a "home run" topology where roadside cabinets only contain patch panels so that all splitters are located centrally. While a 20% higher capital cost could be expected, home run networks may encourage a more competitive wholesale market since providers' equipment can achieve higher use. Internet access IP Connectivity Access Network Local loop Passive Optical Network "The Network Story".
British Telecom. 2005. Archived from the original on 5 May 2010. Interactive presentation introducing the technology and design of access networks
The homing pigeon is a variety of domestic pigeon derived from the rock pigeon, selectively bred for its ability to find its way home over long distances. The wild rock pigeon has an innate homing ability, meaning that it will return to its nest, using magnetoreception; this made it easy to breed from the birds that found their way home over long distances. Flights as long as 1,800 km have been recorded by birds in competitive pigeon racing, their average flying speed over moderate 965 km distances is around 97 km/h and speeds of up to 160 km/h have been observed in top racers for short distances. Because of this skill, homing pigeons were used to carry messages as messenger pigeons, they are referred to as "pigeon post" if used in post service, or "war pigeon" during wars. Homing pigeons are incorrectly categorized as English Carrier pigeons, a breed of fancy pigeons selectively-bred for its distinctively rounded hard wattle; the purpose of using them was to send mails. Male and female pigeons can be differentiated by physical characteristics of the head, beak and breast, though visual identification of sex by physical characteristics alone can be inaccurate.
Males stand taller, have larger beaks, crops and eye ceres, as well as round heads and thicker napes. Females, on the other hand, tend to be shorter with smaller beaks and ceres, as well as flatter heads and fuller breasts. Male and female pigeons show different behaviours; the "coo" of males is louder and more insistent when courting. Display behaviour differs between the sexes. Most notably, a male turns 360 degrees with an inflated crop and a loud "coo", to show interest in a female or to defend or discourage another pigeon from entering its territory, while females never turn full circle, but rather do a 270-degree back-and-forth rotational motion. During breeding season during the warmer months, a male pigeon will court the female by puffing out his chest, bobbing his head and strutting in circles around her, all the while cooing his affections. If she accepts, she will allow him onto her back. After mating, the male will build a nest out of gathered sticks in a suitable crevice, while the female watches and makes changes.
Urban birds will gladly use a roof on a building. The female will lay two eggs; the first egg would be laid late in the evening, the other egg forty hours after, which will hatch in 17 to 20 days, depending on the weather. Both parents aid in rearing the nestlings. Fledglings leave the nest around four to five weeks after hatching; the sport of flying homing pigeons was well-established as early as 3000 years ago. They were used to proclaim the winner of the Ancient Olympics. Messenger pigeons were used as early as 1150 in Baghdad and later by Genghis Khan. By 1167 a regular service between Baghdad and Syria had been established by Sultan Nur ad-Din. In Damietta, by the mouth of the Nile, the Spanish traveller Pedro Tafur saw carrier pigeons for the first time, in 1436, though he imagined that the birds made round trips and back; the Republic of Genoa equipped their system of watch towers in the Mediterranean Sea with pigeon posts. Tipu Sultan of Mysore used homing pigeons; the pigeon holes may be seen in the mosque's minarets to this day.
In 1818, a great pigeon race called. In 1860, Paul Reuter, who founded Reuters press agency, used a fleet of over 45 pigeons to deliver news and stock prices between Brussels and Aachen, the terminus of early telegraph lines; the outcome of the Battle of Waterloo was first delivered by a pigeon to England. During the Franco-Prussian War pigeons were used to carry mail between besieged Paris and the French unoccupied territory. In December 1870, it took ten hours for a pigeon carrying microfilms to fly from Perpignan to Bruxelles. Pigeons carried messages only one way, to their home, they had to be transported manually before another flight. However, by placing their food at one location and their home at another location, pigeons have been trained to fly back and forth up to twice a day reliably, covering round-trip flights up to 160 km, their reliability has lent itself to occasional use on mail routes, such as the Great Barrier Pigeongram Service established between the Auckland, New Zealand, suburb of Newton and Great Barrier Island in November 1897 the first regular air mail service in the world.
The world's first'airmail' stamps were issued for the Great Barrier Pigeon-Gram Service from 1898 to 1908. Homing pigeons were still employed in the 21st century by certain remote police departments in Odisha state in eastern India to provide emergency communication services following natural disasters. In March 2002, it was announced that India's Police Pigeon Service messenger system in Odisha was to be retired, due to the expanded use of the Internet; the Taliban banned use of homing pigeons in Afghanistan. To this day, pigeons are entered into competitions, with the winner receiving prize money at the end. Research has been performed with the intention of discovering how pigeons, after being transported, can find their way back from distant places they have never visited before. Most researchers believe that homing ability is based on a "map and compass" model, with the compass feature allowing birds to orient and the map feature allowing birds to determine their location relative to