A breechloader is a firearm in which the cartridge or shell is inserted or loaded into a chamber integral to the rear portion of a barrel. Modern mass production firearms are breech-loading, except those which are intended by design to be muzzle-loaders, in order to be legal for certain types of hunting. Early firearms, on the other hand, were entirely muzzle-loading; the main advantage of breech-loading is a reduction in reloading time – it is much quicker to load the projectile and the charge into the breech of a gun or cannon than to try to force them down a long tube when the bullet fit is tight and the tube has spiral ridges from rifling. In field artillery, the advantages were similar: the crew no longer had to force powder and shot down a long barrel with rammers, the shot could now fit the bore, without being impossible to ram home with a fouled barrel, it allows turrets and emplacements to be smaller. After breech loading became common, it became common practice to fit recoil systems onto field guns, to prevent the recoil from rolling the carriage back with every shot and ruining the aim.
This allowed for faster firing times, but is not directly related to whether the gun is breech loading or not. Now that guns were able to fire without recoiling, the crew were able to remain grouped around the gun, ready to load and put final touches on the aim, subsequent to firing the next shot; this led to the development of an armored shield fitted to the carriage of the gun, to help shield the crew from long range area or sniper fire from the new, high-velocity, long-range rifles, or machine guns. Although breech-loading firearms were developed as far back as the late 14th century in Burgundy, breech-loading became more successful with improvements in precision engineering and machining in the 19th century; the main challenge for developers of breech-loading firearms was sealing the breech. This was solved for smaller firearms by the development of the self-contained metallic cartridge. For firearms too large to use cartridges, the problem was solved by the development of the interrupted screw.
Breech-loading swivel guns were invented in the 14th century. They were a particular type of swivel gun, consisted in a small breech-loading cannon equipped with a swivel for easy rotation, which could be loaded by inserting a mug-shaped chamber filled with powder and projectiles; the breech-loading swivel gun had a high rate of fire, was effective in anti-personnel roles. Breech-loading firearms are known from the 16th century. Henry VIII possessed one, which he used as a hunting gun to shoot birds. More breech-loading firearms were made in the early 18th century. One such gun known to have belonged to Philip V of Spain, was manufactured circa 1715 in Madrid, it came with a ready-to load reusable cartridge. Patrick Ferguson, a British Army officer, developed in 1772 the Ferguson rifle, a breech-loading flintlock firearm. Two hundred of the rifles were manufactured and used in the Battle of Brandywine, during the American Revolutionary War, but shortly after they were retired and replaced with the standard Brown Bess musket.
On into the mid-19th century there were attempts in Europe at an effective breech-loader. There were concentrated attempts at improved methods of ignition. In Paris in 1808, in association with French gunsmith François Prélat, Jean Samuel Pauly created the first self-contained cartridges: the cartridges incorporated a copper base with integrated mercury fulminate primer powder, a round bullet and either brass or paper casing; the cartridge was fired with a needle. The needle-activated central-fire breech-loading gun would become a major feature of firearms thereafter; the corresponding firearm was developed by Pauly. Pauly made an improved version, protected by a patent on 29 September 1812; the Pauly cartridge was further improved by the French gunsmith Casimir Lefaucheux in 1828, by adding a pinfire primer, but Lefaucheux did not register his patent until 1835: a pinfire cartridge containing powder in a card-board shell. In 1845, another Frenchman Louis-Nicolas Flobert invented, for indoor shooting, the first rimfire metallic cartridge, constituted by a bullet fit in a percussion cap.
Derived in the 6 mm and 9 mm calibres, it is since called the Flobert cartridge but it does not contain any powder. In English-speaking countries the Flobert cartridge corresponds to.22 CB ammunitions. In 1846, yet another Frenchman, Benjamin Houllier, patented the first metallic cartridge containing powder in a metallic shell. Houllier commercialised his weapons in association with the gunsmiths Charles Robert, but the subsequent Houllier and Lefaucheux cartridges if they were the first full-metal shells, were still pinfire cartridges, like those used in the LeMat and Lefaucheux revolvers, although the LeMat evolved in a revolver using rimfire cartridges. The first centrefire cartridge was introduced in 1855 with both Berdan and Boxer priming. In 1842, the Norwegian Armed Forces adopted the breechloading caplock, the Kammerlader, one of the first instances in which a modern army adopted a breechloading rifle as its main infantry firearm; the Dreyse Zündnadelgewehr was a single-shot breech-loading rifle using a rotating bolt to seal the breech.
It was so called because of its.5-inch needle-like firi
A fail-safe in engineering is a design feature or practice that in the event of a specific type of failure, inherently responds in a way that will cause no or minimal harm to other equipment, the environment or to people. Unlike inherent safety to a particular hazard, a system being "fail-safe" does not mean that failure is impossible or improbable, but rather that the system's design prevents or mitigates unsafe consequences of the system's failure; that is, if and when a "fail-safe" system "fails", it is "safe" or at least no less safe than when it was operating correctly. Since many types of failure are possible, failure mode and effects analysis is used to examine failure situations and recommend safety design and procedures; some systems can never be made fail safe. Redundancy, fault tolerance, or recovery procedures are used for these situations; this makes the system less sensitive for the reliability prediction errors or quality induced uncertainty for the separate items. On the other hand, failure detection & correction and avoidance of common cause failures becomes here important to ensure system level reliability.
Examples include: Roller-shutter fire doors – that are activated by building alarm systems or local smoke detectors must close automatically when signaled regardless of power. In case of power outage the coiling fire door does not need to close, but must be capable of automatic closing when given a signal from the building alarm systems or smoke detectors. A temperature sensitive fusible link may be employed to hold the fire doors open against gravity or a closing spring. In case of fire, the link melts and releases the doors, they close; some airport luggage carts – require that one hold down a given cart's handbrake switch at all times. The handbrake-holding requirement thus both operates according to the principles of "fail-safety" and contributes to the fail-security of the system; this is an example of a dead man's switch. Lawnmowers and snow blowers have a hand-closed lever. If it is released, it stops rotor's rotation; this is a dead man's switch. Air brakes on railway trains and air brakes on trucks.
The brakes are held in the "off" position by air pressure created in the brake system. Should a brake line split, or a carriage become de-coupled, the air pressure will be lost and the brakes applied, by springs in the case of trucks, or by a local air reservoir in trains, it is impossible to drive a truck with a serious leak in the air brake system. Motorized gates – In case of power outage the gate can be pushed open by hand with no crank or key required. However, as this would allow anyone to go through the gate, a fail-secure design is used: In a power outage, the gate can only be opened by a hand crank, kept in a safe area or under lock and key; when such a gate provides vehicle access to homes, a fail-safe design is used, where the door opens to allow fire department access. Safety valves – Various devices that operate with fluids use fuses or safety valves as fail-safe mechanisms. A railway semaphore signal is designed so that should the cable controlling the signal break, the arm returns to the "danger" position, preventing any trains passing the inoperative signal.
Isolation valves, control valves – that are used for example in systems containing hazardous substances, can be designed to close upon loss of power, for example by spring force. This is known as fail-closed upon loss of power. An elevator has brakes. If the cable breaks, tension is lost and the brakes latch on, stopping the elevator from falling. Vehicle Air Conditioning – Defrost controls require vacuum for diverter damper operation for all functions except defrost. If vacuum fails, defrost is still available. Examples include: Many devices are protected from short circuit by fuses, circuit breakers, or current limiting circuits; the electrical interruption under overload conditions will prevent damage or destruction of wiring or circuit devices due to overheating. Avionics using redundant systems to perform the same computation using three different systems. Different results indicate a fault in the system. Drive-by-wire and fly-by-wire controls such as an Accelerator Position Sensor have two potentiometers which read in opposite directions, such that moving the control will result in one reading becoming higher, the other equally lower.
Mismatches between the two readings indicates a fault in the system, the ECU can deduce which of the two readings is faulty. Traffic light controllers use a Conflict Monitor Unit to detect faults or conflicting signals and switch an intersection to an all flashing error signal, rather than displaying dangerous conflicting signals, e.g. showing green in all directions. The automatic protection of programs and/or processing systems when a computer hardware or software failure is detected in a computer system. A classic example is a watchdog timer. See Fail-safe. A control operation or function that prevents improper system functioning or catastrophic degradation in the event of circuit malfunction or operator error; the fact that a flashing amber is more permissive than a solid amber on many railway lines is a sign of a failsafe, as the relay, if not working, will revert to a more restrictive setting
In modern English usage, the informal term idiot-proof or foolproof describes designs that cannot be misused either inherently, or by use of defensive design principles. The implication is that the design is usable by someone of low intelligence who would not use it properly; the term "foolproof" originates in 1902. The term "idiot-proof" became popular in the 1970s, it may have been invented as a stronger-sounding version of foolproof, as the force of foolproof had declined due to frequent usage. For the same reason, "foolproof" is now a formal term, whereas "idiot-proof" remains informal. Both terms are adjectives, but can be used as verbs. Several Murphy's law adages claim that idiot-proof systems cannot be made, for example "Nothing is foolproof to a sufficiently talented fool" and "If you make something idiot-proof, someone will just make a better idiot." Along those lines, Douglas Adams wrote in Mostly Harmless, "a common mistake that people make when trying to design something foolproof is to underestimate the ingenuity of complete fools".
Poka-yoke Defensive design Hanlon's razor Inherent safety Unintended consequences
An elevator or lift is a type of vertical transportation device that moves people or goods between floors of a building, vessel, or other structure. Elevators are powered by electric motors that drive traction cables and counterweight systems like a hoist, although some pump hydraulic fluid to raise a cylindrical piston like a jack. In agriculture and manufacturing, an elevator is any type of conveyor device used to lift materials in a continuous stream into bins or silos. Several types exist, such as the chain and bucket elevator, grain auger screw conveyor using the principle of Archimedes' screw, or the chain and paddles or forks of hay elevators. Languages other than English may lift; because of wheelchair access laws, elevators are a legal requirement in new multistory buildings where wheelchair ramps would be impractical. There are some elevators which can go sideways in addition to the usual up-and-down motion; the earliest known reference to an elevator is in the works of the Roman architect Vitruvius, who reported that Archimedes built his first elevator in 236 BC.
Some sources from historical periods mention elevators as cabs on a hemp rope powered by hand or by animals. In 1000, the Book of Secrets by al-Muradi in Islamic Spain described the use of an elevator-like lifting device, in order to raise a large battering ram to destroy a fortress. In the 17th century the prototypes of elevators were located in the palace buildings of England and France. Louis XV of France had a so-called'flying chair' built for one of his mistresses at the Chateau de Versailles in 1743. Ancient and medieval elevators used drive systems based on windlasses; the invention of a system based on the screw drive was the most important step in elevator technology since ancient times, leading to the creation of modern passenger elevators. The first screw drive elevator was built by Ivan Kulibin and installed in the Winter Palace in 1793. Several years another of Kulibin's elevators was installed in the Arkhangelskoye near Moscow; the development of elevators was led by the need for movement of raw materials including coal and lumber from hillsides.
The technology developed by these industries and the introduction of steel beam construction worked together to provide the passenger and freight elevators in use today. Starting in the coal mines, by the mid-19th century elevators were operated with steam power and were used for moving goods in bulk in mines and factories; these steam driven devices were soon being applied to a diverse set of purposes—in 1823, two architects working in London and Hormer, built and operated a novel tourist attraction, which they called the "ascending room". It elevated paying customers to a considerable height in the center of London, allowing them a magnificent panoramic view of downtown. Early, crude steam-driven elevators were refined in the ensuing decade; the elevator used a counterweight for extra power. The hydraulic crane was invented by Sir William Armstrong in 1846 for use at the Tyneside docks for loading cargo; these supplanted the earlier steam driven elevators: exploiting Pascal's law, they provided a much greater force.
A water pump supplied a variable level of water pressure to a plunger encased inside a vertical cylinder, allowing the level of the platform to be raised and lowered. Counterweights and balances were used to increase the lifting power of the apparatus. Henry Waterman of New York is credited with inventing the "standing rope control" for an elevator in 1850. In 1845, the Neapolitan architect Gaetano Genovese installed in the Royal Palace of Caserta the "Flying Chair", an elevator ahead of its time, covered with chestnut wood outside and with maple wood inside, it included a light, two benches and a hand operated signal, could be activated from the outside, without any effort on the part of the occupants. Traction was controlled by a motor mechanic utilizing a system of toothed wheels. A safety system was designed to take effect, it consisted of a beam pushed outwards by a steel spring. In 1852, Elisha Otis introduced the safety elevator, which prevented the fall of the cab if the cable broke, he demonstrated it at the New York exposition in the Crystal Palace in a dramatic, death-defying presentation in 1854, the first such passenger elevator was installed at 488 Broadway in New York City on 23 March 1857.
The first elevator shaft preceded the first elevator by four years. Construction for Peter Cooper's Cooper Union Foundation building in New York began in 1853. An elevator shaft was included in the design, because Cooper was confident that a safe passenger elevator would soon be invented; the shaft was cylindrical. Otis designed a special elevator for the building; the Equitable Life Building completed in 1870 in New York City was thought to be the first office building to have passenger elevators. However Peter Ellis, an English architect, installed the first elevators that could be described as paternoster elevators in Oriel Chambers in Liverpool in 1868; the first electric elevator was built by Werner von Siemens in 1880 in Germany. The inventor Anton Freissler developed the ideas of von Siemens and built up a successful enterprise in Austria-Hungary; the safety and speed of electric elevators were enhanced by Frank Sprague who added floor control, automatic elevators, acceleration control of cars, safeties.
His elevator ran faster and with larger loads than hyd
Lockout-tagout or lock and tag is a safety procedure used in industry and research settings to ensure that dangerous machines are properly shut off and not able to be started up again prior to the completion of maintenance or repair work. It requires that hazardous energy sources be "isolated and rendered inoperative" before work is started on the equipment in question; the isolated power sources are locked and a tag is placed on the lock identifying the worker who placed it. The worker holds the key for the lock, ensuring that only he or she can remove the lock and start the machine; this prevents accidental startup of a machine while it is in a hazardous state or while a worker is in direct contact with it. Lockout-tagout is used across industries as a safe method of working on hazardous equipment and is mandated by law in some countries. Machinery can contain many hazards to workers, such as: Electricity Hydraulic pressure Pneumatic pressure Radiation - intense visible light or thermal radiation, as well as ionizing radiation or charged particle beams Extremely hot or cold surfaces, which may cause burns Liquids - gasoline or other fuels and water Gases - poisonous and explosive Steam Gravity - falls from height, falling parts, or mechanisms that work with or against it Spring tension Moving parts - fans, gears, saw blades, pressesFor example, a single industrial device may contain hot fluids, blades, electrical heaters, conveyor belts with pinch points, moving chains, ultraviolet light.
Disconnecting or making safe the equipment involves the removal of all energy sources and is known as isolation. The steps necessary to isolate equipment are documented in an isolation procedure or a lockout tagout procedure; the isolation procedure includes the following tasks: Announce shut off Identify the energy source Isolate the energy source Lock and tag the energy source Prove that the equipment isolation is effectiveThe locking and tagging of the isolation point lets others know not to de-isolate the device. To emphasize the last step above in addition to the others, the entire process can be referred to as lock and try; the National Electric Code states that a safety/service disconnect must be installed within sight of serviceable equipment. The safety disconnect ensures the equipment can be isolated and there is less chance of someone turning the power back on if they can see the work going on; these safety disconnects have multiple places for locks so more than one person can work on equipment safely.
In industrial processes it can be difficult to establish where the appropriate danger sources might be. For example, a food processing plant may have input and output tanks and high-temperature cleaning systems connected, but not in the same room or area of the factory, it would not be unusual to have to visit several areas of the factory in order to isolate a device for service. Safety equipment manufacturers provide a range of isolation devices designed to fit various switches and effectors. For example, most circuit breakers have a provision to have a small padlock attached to prevent their activation. For other devices such as ball or gate valves, plastic pieces which either fit against the pipe and prevent movement, or clamshell-style objects which surround the valve and prevent its manipulation are used. A common feature of these devices is their bright color red, to increase visibility and allow workers to see if a device is isolated; the devices are of such a design and construction to prevent it being removed with any moderate force - for example, an isolation device does not have to resist a chainsaw, but if an operator forcibly removes it, it will be visible that it has been tampered with.
To protect one or more circuit breakers in an electrical panel, a lockout-tagout device called the Panel Lockout can be used. It keeps the panel door prevents the panel cover from being removed; the circuit breakers remain in the off position. When two or more people are working on the same or different parts of a larger overall system, there must be multiple holes to lock the device. To expand the number of available holes, the lockout device is secured with a folding scissors clamp that has many pairs of padlock holes capable of keeping it closed; each worker applies their own padlock to the clamp. The locked-out machinery cannot be activated until all workers have removed their padlocks from the clamp. In the United States a lock selected by color, shape or size, such as a red padlock, is used to designate a standard safety device and securing hazardous energy. No two keys or locks should be the same. A person's lock and tag must only be removed by the individual who installed the lock and tag unless removal is accomplished under the direction of the employer.
Employer procedures and training for such removal must have been developed and incorporated into the employer energy control program. By US Federal regulation 29 CFR 1910.147 the tag must have an identification showing the name of the person doing the lock and tag. While this may be true for the United States, it is not mandatory in Europe; the lockout can be done by a "role" such as the shift leader. Using a "lockbox", the shift leader is always the last one to remove the lock and has to verify it is safe to start up equipment. According to the European standard EN 50110-1, the safety procedure before working on electric equipment comprises the follo
In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components and software, including communication protocols. Early computer buses were parallel electrical wires with multiple hardware connections, but the term is now used for any physical arrangement that provides the same logical function as a parallel electrical bus. Modern computer buses can use both parallel and bit serial connections, can be wired in either a multidrop or daisy chain topology, or connected by switched hubs, as in the case of USB. Computer systems consist of three main parts: the central processing unit that processes data, memory that holds the programs and data to be processed, I/O devices as peripherals that communicate with the outside world. An early computer might contain a hand-wired CPU of vacuum tubes, a magnetic drum for main memory, a punch tape and printer for reading and writing data respectively.
A modern system might have a multi-core CPU, DDR4 SDRAM for memory, a solid-state drive for secondary storage, a graphics card and LCD as a display system, a mouse and keyboard for interaction, a Wi-Fi connection for networking. In both examples, computer buses of one form or another move data between all of these devices. In most traditional computer architectures, the CPU and main memory tend to be coupled. A microprocessor conventionally is a single chip which has a number of electrical connections on its pins that can be used to select an "address" in the main memory and another set of pins to read and write the data stored at that location. In most cases, the CPU and memory share signalling operate in synchrony; the bus connecting the CPU and memory is one of the defining characteristics of the system, referred to as the system bus. It is possible to allow peripherals to communicate with memory in the same fashion, attaching adaptors in the form of expansion cards directly to the system bus.
This is accomplished through some sort of standardized electrical connector, several of these forming the expansion bus or local bus. However, as the performance differences between the CPU and peripherals varies some solution is needed to ensure that peripherals do not slow overall system performance. Many CPUs feature a second set of pins similar to those for communicating with memory, but able to operate at different speeds and using different protocols. Others use smart controllers to place the data directly in memory, a concept known as direct memory access. Most modern systems combine both solutions; as the number of potential peripherals grew, using an expansion card for every peripheral became untenable. This has led to the introduction of bus systems designed to support multiple peripherals. Common examples are the SATA ports in modern computers, which allow a number of hard drives to be connected without the need for a card. However, these high-performance systems are too expensive to implement in low-end devices, like a mouse.
This has led to the parallel development of a number of low-performance bus systems for these solutions, the most common example being the standardized Universal Serial Bus. All such examples may be referred to as peripheral buses, although this terminology is not universal. In modern systems the performance difference between the CPU and main memory has grown so great that increasing amounts of high-speed memory is built directly into the CPU, known as a cache. In such systems, CPUs communicate using high-performance buses that operate at speeds much greater than memory, communicate with memory using protocols similar to those used for peripherals in the past; these system buses are used to communicate with most other peripherals, through adaptors, which in turn talk to other peripherals and controllers. Such systems are architecturally more similar to multicomputers, communicating over a bus rather than a network. In these cases, expansion buses are separate and no longer share any architecture with their host CPU.
What would have been a system bus is now known as a front-side bus. Given these changes, the classical terms "system", "expansion" and "peripheral" no longer have the same connotations. Other common categorization systems are based on the bus's primary role, connecting devices internally or externally, PCI vs. SCSI for instance. However, many common modern bus systems can be used for both. Other examples, like InfiniBand and I²C were designed from the start to be used both internally and externally; the internal bus known as internal data bus, memory bus, system bus or Front-Side-Bus, connects all the internal components of a computer, such as CPU and memory, to the motherboard. Internal data buses are referred to as a local bus, because they are intended to connect to local devices; this bus is rather quick and is independent of the rest of the computer operations. The external bus, or expansion bus, is made up of the electronic pathways that connect the different external devices, such as printer etc. to the computer.
Buses can be parallel buses, which carry data words in parallel on multiple wires, or serial buses, which carry data in bit-serial form. The addition of extra power and control connections, differential
A finite-state machine or finite-state automaton, finite automaton, or a state machine, is a mathematical model of computation. It is an abstract machine that can be in one of a finite number of states at any given time; the FSM can change from one state to another in response to some external inputs. An FSM is defined by a list of its states, its initial state, the conditions for each transition. Finite state machines are of two types – deterministic finite state machines and non-deterministic finite state machines. A deterministic finite-state machine can be constructed equivalent to any non-deterministic one; the behavior of state machines can be observed in many devices in modern society that perform a predetermined sequence of actions depending on a sequence of events with which they are presented. Simple examples are vending machines, which dispense products when the proper combination of coins is deposited, whose sequence of stops is determined by the floors requested by riders, traffic lights, which change sequence when cars are waiting, combination locks, which require the input of combination numbers in the proper order.
The finite state machine has less computational power than some other models of computation such as the Turing machine. The computational power distinction means there are computational tasks that a Turing machine can do but a FSM cannot; this is because a FSM's memory is limited by the number of states it has. FSMs are studied in the more general field of automata theory. An example of a simple mechanism that can be modeled by a state machine is a turnstile. A turnstile, used to control access to subways and amusement park rides, is a gate with three rotating arms at waist height, one across the entryway; the arms are locked, blocking the entry, preventing patrons from passing through. Depositing a coin or token in a slot on the turnstile unlocks the arms, allowing a single customer to push through. After the customer passes through, the arms are locked again. Considered as a state machine, the turnstile has two possible states: Unlocked. There are two possible inputs that affect its state: pushing the arm.
In the locked state, pushing on the arm has no effect. Putting a coin in – that is, giving the machine a coin input – shifts the state from Locked to Unlocked. In the unlocked state, putting additional coins in has no effect. However, a customer pushing through the arms, giving a push input, shifts the state back to Locked; the turnstile state machine can be represented by a state transition table, showing for each possible state, the transitions between them and the outputs resulting from each input: The turnstile state machine can be represented by a directed graph called a state diagram. Each state is represented by a node. Edges show the transitions from one state to another; each arrow is labeled with the input. An input that doesn't cause a change of state is represented by a circular arrow returning to the original state; the arrow into the Locked node from the black dot indicates. A state is a description of the status of a system, waiting to execute a transition. A transition is a set of actions to be executed when a condition is fulfilled or when an event is received.
For example, when using an audio system to listen to the radio, receiving a "next" stimulus results in moving to the next station. When the system is in the "CD" state, the "next" stimulus results in moving to the next track. Identical stimuli trigger different actions depending on the current state. In some finite-state machine representations, it is possible to associate actions with a state: an entry action: performed when entering the state, an exit action: performed when exiting the state. Several state transition table types are used; the most common representation is shown below: the combination of current state and input shows the next state. The complete action's information is not directly described in the table and can only be added using footnotes. A FSM definition including the full actions information is possible using state tables; the Unified Modeling Language has a notation for describing state machines. UML state machines overcome the limitations of traditional finite state machines while retaining their main benefits.
UML state machines introduce the new concepts of hierarchically nested states and orthogonal regions, while extending the notion of actions. UML state machines have the characteristics of Moore machines, they support actions that depend on both the state of the system and the triggering event, as in Mealy machines, as well as entry and exit actions, which are associated with states rather than transitions, as in Moore machines. The Specification and Description Language is a standard from ITU that includes graphical symbols to describe actions in the transition: send an event receive an event start a timer cancel a timer start another concurrent state machine decisionSDL embeds basic data types called "Abstract Data Types", an action language, an execution semantic in order to make the finite state machine executable. There are a large number of variants to represent an FSM such as the one in figure 3. In addition to their use in modeling reactive systems