romikgosai/squad_modified huggingface dataset:
In 1852, Elisha Otis introduced the safety elevator, which prevented the fall of the cab if the cable broke. The design of the Otis safety elevator is somewhat similar to one type still used today. A governor device engages knurled roller(s), locking the elevator to its guides should the elevator descend at excessive speed. He demonstrated it at the New York exposition in the Crystal Palace in a dramatic, death-defying presentation in 1854, and the first such passenger elevator was installed at 488 Broadway in New York City on March 23, 1857.

Questions and answers:
['
Q: Who created the safety elevator in 1852?
A: Elisha Otis', '
Q: What feature did the safety elevator display? 
A: prevented the fall of the cab if the cable broke', '
Q: What did the govenor device engage to lock the elevator?
A: knurled roller(s)', '
Q: At what location was it first presented?
A: New York exposition in the Crystal Palace', '
Q: Where was the first safety elevator installed?
A: 488 Broadway in New York City']
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 because Cooper thought it was the most efficient design. Later, Otis designed a special elevator for the building. Today the Otis Elevator Company, now a subsidiary of United Technologies Corporation, is the world's largest manufacturer of vertical transport systems.

Questions and answers:
['
Q: Which was built first, the first elevator shaft or the first elevator?
A: first elevator shaft', '
Q: What year did constructrion begin for the Cooper Union Foundation?
A: 1853', '
Q: What design did Peter Cooper feel was the most efficient?
A: cylindrical', '
Q: The Otis Elevator Company is today a subsidiary of what major corporation?
A: United Technologies Corporation', "
Q: What title does United Technologies Corporation hold?
A: world's largest manufacturer of vertical transport systems"]
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 significantly enhanced by Frank Sprague who added floor control, automatic elevators, acceleration control of cars, and safeties. His elevator ran faster and with larger loads than hydraulic or steam elevators, and 584 electric elevators were installed before Sprague sold his company to the Otis Elevator Company in 1895. Sprague also developed the idea and technology for multiple elevators in a single shaft.

Questions and answers:
['
Q: Who built the first electric elevator?
A: Werner von Siemens', '
Q: The first electric elevator, built in 1880, was in what Country?
A: Germany', '
Q: Who is credited with increasing the safety and speed of electric elevators?
A: Frank Sprague', '
Q: Who ultilized von Siemens ideas to build a succesful business?
A: Anton Freissler', '
Q: To whom did Frank Sprague sell his company to in 1895?
A: Otis Elevator Company']
Some people argue that elevators began as simple rope or chain hoists (see Traction elevators below). An elevator is essentially a platform that is either pulled or pushed up by a mechanical means. A modern-day elevator consists of a cab (also called a "cage", "carriage" or "car") mounted on a platform within an enclosed space called a shaft or sometimes a "hoistway". In the past, elevator drive mechanisms were powered by steam and water hydraulic pistons or by hand. In a "traction" elevator, cars are pulled up by means of rolling steel ropes over a deeply grooved pulley, commonly called a sheave in the industry. The weight of the car is balanced by a counterweight. Sometimes two elevators are built so that their cars always move synchronously in opposite directions, and are each other's counterweight.

Questions and answers:
['
Q: What is another name for an elevator shaft?
A: hoistway', '
Q: Elevator drive mechanisms have, in the past been, powered by what?
A: steam and water hydraulic pistons or by hand', '
Q: What is the weight of the elevator cage balanced by? 
A: a counterweight', '
Q: How do elevators built in pairs work?
A: their cars always move synchronously in opposite directions,']
Elevator doors protect riders from falling into the shaft. The most common configuration is to have two panels that meet in the middle, and slide open laterally. In a cascading telescopic configuration (potentially allowing wider entryways within limited space), the doors roll on independent tracks so that while open, they are tucked behind one another, and while closed, they form cascading layers on one side. This can be configured so that two sets of such cascading doors operate like the center opening doors described above, allowing for a very wide elevator cab. In less expensive installations the elevator can also use one large "slab" door: a single panel door the width of the doorway that opens to the left or right laterally. Some buildings have elevators with the single door on the shaft way, and double cascading doors on the cab.

Questions and answers:
['
Q: How do most elevator doors work?
A: have two panels that meet in the middle, and slide open laterally', '
Q: What is a single panel door referred to as?
A: "slab" door', '
Q: What design allows wider entryways within limited space?
A: a cascading telescopic configuration', '
Q: The single door is sometimes located where?
A: on the shaft way', '
Q: What do elevator doors protect riders from?
A: falling into the shaft']
Historically, AC motors were used for single or double speed elevator machines on the grounds of cost and lower usage applications where car speed and passenger comfort were less of an issue, but for higher speed, larger capacity elevators, the need for infinitely variable speed control over the traction machine becomes an issue. Therefore, DC machines powered by an AC/DC motor generator were the preferred solution. The MG set also typically powered the relay controller of the elevator, which has the added advantage of electrically isolating the elevators from the rest of a building's electrical system, thus eliminating the transient power spikes in the building's electrical supply caused by the motors starting and stopping (causing lighting to dim every time the elevators are used for example), as well as interference to other electrical equipment caused by the arcing of the relay contactors in the control system.

Questions and answers:
['
Q: Throughout history, what type of engines were used for elevator machines?
A: AC motors', '
Q: Why were AC motors used?
A: cost and lower usage applications where car speed and passenger comfort were less of an issue', '
Q: What problem arises for fast and large capacity elevators?
A: the need for infinitely variable speed control over the traction machine', '
Q: Generally, what powered the relay contoller?
A: MG set', "
Q: What is a known advantage of the MG set?
A: electrically isolating the elevators from the rest of a building's electrical system"]
Gearless traction machines are low-speed (low-RPM), high-torque electric motors powered either by AC or DC. In this case, the drive sheave is directly attached to the end of the motor. Gearless traction elevators can reach speeds of up to 20 m/s (4,000 ft/min), A brake is mounted between the motor and gearbox or between the motor and drive sheave or at the end of the drive sheave to hold the elevator stationary at a floor. This brake is usually an external drum type and is actuated by spring force and held open electrically; a power failure will cause the brake to engage and prevent the elevator from falling (see inherent safety and safety engineering). But it can also be some form of disc type like 1 or more calipers over a disc in one end of the motor shaft or drive sheave which is used in high speed, high rise and large capacity elevators with machine rooms(an exception is the Kone MonoSpace's EcoDisc which is not high speed, high rise and large capacity and is machine room less but it uses the same design as is a thinner version of a conventional gearless traction machine) for breaking power, compactness and redundancy(assuming there's at least 2 calipers on the disc), or 1 or more disc brakes with a single caliper at one end of the motor shaft or drive sheave which is used in machine room less elevators for compactness, breaking power, and redundancy(assuming there's 2 brakes or more).

Questions and answers:
['
Q: In a gearless traction engine, what is the drive sheave attached to?
A: directly attached to the end of the motor', '
Q: What speed is a gearless traction elevator capable of attaining?
A: 20 m/s (4,000 ft/min)', '
Q: What motivates an external drum brake held open electrically?
A: spring force', "
Q: One exception that is not high speed high rise and large capacity is what?
A: Kone MonoSpace's EcoDisc"]
In each case, cables are attached to a hitch plate on top of the cab or may be "underslung" below a cab, and then looped over the drive sheave to a counterweight attached to the opposite end of the cables which reduces the amount of power needed to move the cab. The counterweight is located in the hoist-way and rides a separate railway system; as the car goes up, the counterweight goes down, and vice versa. This action is powered by the traction machine which is directed by the controller, typically a relay logic or computerized device that directs starting, acceleration, deceleration and stopping of the elevator cab. The weight of the counterweight is typically equal to the weight of the elevator cab plus 40-50% of the capacity of the elevator. The grooves in the drive sheave are specially designed to prevent the cables from slipping. "Traction" is provided to the ropes by the grip of the grooves in the sheave, thereby the name. As the ropes age and the traction grooves wear, some traction is lost and the ropes must be replaced and the sheave repaired or replaced. Sheave and rope wear may be significantly reduced by ensuring that all ropes have equal tension, thus sharing the load evenly. Rope tension equalization may be achieved using a rope tension gauge, and is a simple way to extend the lifetime of the sheaves and ropes.

Questions and answers:
['
Q: What reduces the amount of force needed to propel the cab?
A: cables are attached to a hitch plate on top of the cab', '
Q: Where will the counterweight be found?
A: in the hoist-way', '
Q: What guides the traction machine?
A: the controller', '
Q: The counterweight runs equal to the cab weight plus what percentage of the elevator capacity?
A: 40-50%', '
Q: Maintaining that the ropes all have equal tension may reduce what?
A: Sheave and rope wear']
Elevators with more than 30 m (98 ft) of travel have a system called compensation. This is a separate set of cables or a chain attached to the bottom of the counterweight and the bottom of the elevator cab. This makes it easier to control the elevator, as it compensates for the differing weight of cable between the hoist and the cab. If the elevator cab is at the top of the hoist-way, there is a short length of hoist cable above the car and a long length of compensating cable below the car and vice versa for the counterweight. If the compensation system uses cables, there will be an additional sheave in the pit below the elevator, to guide the cables. If the compensation system uses chains, the chain is guided by a bar mounted between the counterweight railway lines.

Questions and answers:
['
Q: "Compensation" is the name of the system used for what type of elevators?
A: Elevators with more than 30 m (98 ft) of travel', '
Q: "Compensation" consists of what?
A: a separate set of cables or a chain attached to the bottom of the counterweight and the bottom of the elevator cab', '
Q: What is the chain guided by in a compensation system that uses chains?
A: a bar mounted between the counterweight railway lines', '
Q: What exactly does this system compensate for?
A: the differing weight of cable between the hoist and the cab']
The low mechanical complexity of hydraulic elevators in comparison to traction elevators makes them ideal for low rise, low traffic installations. They are less energy efficient as the pump works against gravity to push the car and its passengers upwards; this energy is lost when the car descends on its own weight. The high current draw of the pump when starting up also places higher demands on a building’s electrical system. There are also environmental concerns should the lifting cylinder leak fluid into the ground.

Questions and answers:
['
Q: What type of installations are hydraulic elevators best suited for?
A: low rise, low traffic installations', '
Q: Why do hydraulic elevators use more energy?
A: the pump works against gravity to push the car and its passengers upwards; this energy is lost when the car descends on its own weight', '
Q: What else contributes to a higher demand from the electrical system?
A: The high current draw of the pump when starting up', '
Q: What concerns arise when the lifting cylinder leaks fluid into the ground?
A: environmental concerns']
A climbing elevator is a self-ascending elevator with its own propulsion. The propulsion can be done by an electric or a combustion engine. Climbing elevators are used in guyed masts or towers, in order to make easy access to parts of these constructions, such as flight safety lamps for maintenance. An example would be the Moonlight towers in Austin, Texas, where the elevator holds only one person and equipment for maintenance. The Glasgow Tower — an observation tower in Glasgow, Scotland — also makes use of two climbing elevators.

Questions and answers:
['
Q: What defines a climbing elevator?
A: a self-ascending elevator with its own propulsion', '
Q: What settings are climbing elevators used in?
A: guyed masts or towers', '
Q: What is the Glasgow Tower?
A: an observation tower in Glasgow, Scotland', '
Q: How is the propulsion powered in a climbing elevator?
A: by an electric or a combustion engine']
A elevator of this kind uses a vacuum on top of the cab and a valve on the top of the "shaft" to move the cab upwards and closes the valve in order to keep the cab at the same level. a diaphragm or a piston is used as a "brake" if there's a sudden increase in pressure avove the cab. however, to go down, it opens the valve so that the air can pressurize the top of the "shaft", allowing the cab to go down by its own weight. this also means that in case of a power failure, the cab will automatically go down. the "shaft" is made of acrilic, is always round, due to the shape of the vacuum pump turbine. in order to keep the air inside of the cab, rubber seals are used. due to technical limitations, these elevators have a low capacity. they usually allow 1-3 passengers and up to 525 lbs.

Questions and answers:
['
Q: What does this type of elevator use to propel the cage?
A: a vacuum on top of the cab and a valve on the top of the "shaft"', '
Q: For sudden surges in pressure above the cab, what is used as a "brake"?
A: a diaphragm or a piston', '
Q: How does it enable the cab to go down by it\'s own weight?
A: it opens the valve so that the air can pressurize the top of the "shaft"', '
Q: What is the shaft made of?
A: acrilic', '
Q: How much weight is permitted on a low capacity elevator?
A: up to 525 lbs']
In the first half of the twentieth century, almost all elevators had no automatic positioning of the floor on which the cab would stop. Some of the older freight elevators were controlled by switches operated by pulling on adjacent ropes. In general, most elevators before WWII were manually controlled by elevator operators using a rheostat connected to the motor. This rheostat (see picture) was enclosed within a cylindrical container about the size and shape of a cake. This was mounted upright or sideways on the cab wall and operated via a projecting handle, which was able to slide around the top half of the cylinder.

Questions and answers:
['
Q: Until the mid 1900s most elevators lacked what?
A: automatic positioning of the floor on which the cab would stop', '
Q: How were most elevators built before 1939 powered? 
A: by elevator operators using a rheostat connected to the motor', '
Q:  Many earlier built  freight elevators were controlled by what?
A: switches operated by pulling on adjacent ropes', '
Q: A rheostat is the size and shape of what?
A: a cake', '
Q: Where was the rheostat mounted?
A: upright or sideways on the cab wall']
The elevator motor was located at the top of the shaft or beside the bottom of the shaft. Pushing the handle forward would cause the cab to rise; backwards would make it sink. The harder the pressure, the faster the elevator would move. The handle also served as a dead man switch: if the operator let go of the handle, it would return to its upright position, causing the elevator cab to stop. In time, safety interlocks would ensure that the inner and outer doors were closed before the elevator was allowed to move.

Questions and answers:
['
Q: Where is the elevator motor found?
A: at the top of the shaft or beside the bottom of the shaft', '
Q: Moving the helve forward causes the cab to do what?
A: to rise', '
Q: The more pressure applied to the handle caused what?
A: the faster the elevator would move', '
Q: Why was the handle considered a "dead man switch"?
A: if the operator let go of the handle, it would return to its upright position, causing the elevator cab to stop', '
Q: Eventually safety locks were used to guarantee what?
A: that the inner and outer doors were closed before the elevator was allowed to move']
Some skyscraper buildings and other types of installation feature a destination operating panel where a passenger registers their floor calls before entering the car. The system lets them know which car to wait for, instead of everyone boarding the next car. In this way, travel time is reduced as the elevator makes fewer stops for individual passengers, and the computer distributes adjacent stops to different cars in the bank. Although travel time is reduced, passenger waiting times may be longer as they will not necessarily be allocated the next car to depart. During the down peak period the benefit of destination control will be limited as passengers have a common destination.

Questions and answers:
['
Q: What function does a "destination operating panel" feature?
A: a passenger registers their floor calls before entering the car', '
Q: What is another benefit of a "destination operating panel"?
A: the computer distributes adjacent stops to different cars in the bank', '
Q: What is one benefit of a "destination operating panel"
A: travel time is reduced as the elevator makes fewer stops for individual passengers', '
Q: What is the downside to a :destination operating panel"?
A: passenger waiting times may be longer as they will not necessarily be allocated the next car to depart']
However, performance enhancements cannot be generalized as the benefits and limitations of the system are dependent on many factors. One problem is that the system is subject to gaming. Sometimes, one person enters the destination for a large group of people going to the same floor. The dispatching algorithm is usually unable to completely cater for the variation, and latecomers may find the elevator they are assigned to is already full. Also, occasionally, one person may press the floor multiple times. This is common with up/down buttons when people believe this to be an effective way to hurry elevators. However, this will make the computer think multiple people are waiting and will allocate empty cars to serve this one person.

Questions and answers:
['
Q: What is one example of a limitation on the system? 
A: the system is subject to gaming', '
Q: What is generally unable to support variations in the number of people for a particular destination?
A: The dispatching algorithm', '
Q: For what reason do people repeatedly push the up/down buttons on a panel?
A: people believe this to be an effective way to hurry elevators', '
Q: Why is this a bad practice?
A: this will make the computer think multiple people are waiting and will allocate empty cars to serve this one person']
To prevent this problem, in one implementation of destination control, every user gets an RFID card to identify himself, so the system knows every user call and can cancel the first call if the passenger decides to travel to another destination to prevent empty calls. The newest invention knows even where people are located and how many on which floor because of their identification, either for the purposes of evacuating the building or for security reasons. Another way to prevent this issue is to treat everyone travelling from one floor to another as one group and to allocate only one car for that group.

Questions and answers:
['
Q: What is one way to implement destination control?
A: every user gets an RFID card to identify himself', '
Q: How does this help the system?
A: the system knows every user call and can cancel the first call if the passenger decides to travel to another destination to prevent empty calls', '
Q: Newer systems know where and how many people are at a location for what reasons?
A: either for the purposes of evacuating the building or for security reasons']
During up-peak mode (also called moderate incoming traffic), elevator cars in a group are recalled to the lobby to provide expeditious service to passengers arriving at the building, most typically in the morning as people arrive for work or at the conclusion of a lunch-time period. Elevators are dispatched one-by-one when they reach a pre-determined passenger load, or when they have had their doors opened for a certain period of time. The next elevator to be dispatched usually has its hall lantern or a "this car leaving next" sign illuminated to encourage passengers to make maximum use of the available elevator system capacity. Some elevator banks are programmed so that at least one car will always return to the lobby floor and park whenever it becomes free.

Questions and answers:
['
Q: What is another name for up-peak mode?
A: moderate incoming traffic', '
Q: Generally, up-peak mode takes place during what times of the day?
A: most typically in the morning', '
Q: What are the reasons for up-peak mode early in the day?
A: people arrive for work or at the conclusion of a lunch-time period', '
Q: For what reasons are elevators routed one-by-one?
A: when they reach a pre-determined passenger load, or when they have had their doors opened for a certain period of time', '
Q: Why is a "this car leaving next" sign used?
A: to encourage passengers to make maximum use of the available elevator system capacity']
Independent service is a special service mode found on most elevators. It is activated by a key switch either inside the elevator itself or on a centralized control panel in the lobby. When an elevator is placed on independent service, it will no longer respond to hall calls. (In a bank of elevators, traffic is rerouted to the other elevators, while in a single elevator, the hall buttons are disabled). The elevator will remain parked on a floor with its doors open until a floor is selected and the door close button is held until the elevator starts to travel. Independent service is useful when transporting large goods or moving groups of people between certain floors.

Questions and answers:
['
Q: How is the special sercice mode enabled?
A: by a key switch either inside the elevator itself or on a centralized control panel in the lobby', '
Q: What is the impact on an elevator set to independant service mode?
A: it will no longer respond to hall calls', '
Q: At what times is Independant service best utilized?
A: when transporting large goods or moving groups of people between certain floors', '
Q: During independant service mode how is a single cab in a hall kept from being used?
A: the hall buttons are disabled']