Elevator

:This article is about the transport device. For other meanings of the word, see Elevator (disambiguation).

Controlling elevators

General controls

A typical modern passenger elevator will have:

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• Call buttons to choose a floor. Some of these may be key switches (to control access). In some elevators, certain floors are inaccessible unless one swipes a security card or enters a passcode (or both).
• Door open and door close buttons to instruct the elevator to close immediately or remain open longer. In some elevators, holding the door open for too long will trigger an audible alarm (This alarm might confuse some people to think that the elevator is overloaded).
• A stop switch to halt the elevator (often used to hold an elevator open while freight is loaded). Keeping an elevator stopped for too long may trigger an alarm. Often, this will be a key switch.
• An alarm button or switch, which passengers can use to signal that they have been trapped in the elevator.

Some elevators may have one or more of the following:

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• An elevator telephone, which can be used (in addition to the alarm) by a trapped passenger to call for help.
• A fireman's key switch, which places the elevator in a special operating mode designed to aid firefighters.
• A medical emergency key switch, which places the elevator in a special operating mode designed to aid medical personnel.

Other controls, which are generally inaccessible to the public (either because they are key switches, or because they are kept behind a locked panel, include:

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• Switches to control the lights and ventilation fans in the elevator.
• An inspector's switch, which places the elevator in inspection mode.
• An independent service switch, which selects whether the elevator's operation will be coordinated with other elevators in an elevator bank.
• Up and down buttons, to move the car up and down without selecting a specific floor. Some older elevators can only be operated this way.

Controls in early elevators

• Some older freight elevators are controlled by switches operated by pulling on adjacent ropes. Safety interlocks ensure that the inner and outer doors are closed before the elevator is allowed to move.
• Early elevators had no automatic landing positioning. Elevators were operated by elevator operators using a motor controller. The controller was contained within a cylindrical container about the size and shape of a cake container and this was operated via a projecting handle. This allowed some control over the energy supplied to the motor (located at the top of the elevator shaft) and so enabled the elevator to be accurately positioned — if the operator was sufficiently skilled. More typically the operator would have to "jog" the control to get the elevator reasonably close to the landing point and then direct the outgoing and incoming passengers to "watch the step". Such elevators did not contain inner doors, as the landing had to be visible for proper positioning of the cab. After stopping at the landing the operator would reach over and pull an attached lever to open the landing doors. Manually operated elevators were generally refitted or the cabs replaced by automatic equipment by the 1950's.
• Large buildings with multiple elevators of this type would also have an elevator dispatcher stationed in the lobby to direct passengers and to signal the operator to leave with the use of a mechanical "cricket" noisemaker.
• Some elevators still in operation have pushbutton manual controls; an example is in a thumbnail on this page. .

Floor numbering

In general, elevator call buttons are numbered one-by-one to indicate the floors or landings that they cause the car to move to. However, there are some conventions to be aware of. The most important are:

Related Topics:
Button - Floor - Landing

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• The differences in floor numbering between different cultures, such as the numbering system used by the USA and in China as compared with the conventions set by the British.
• Floor numbers considered unlucky may be skipped; the example, the floor above 12 may be numbered 14. Another example is skipping the 4th floor in Japan or Korea, as this number is sometimes considered unlucky.
• The top level may be PH for Penthouse or, where applicable, R for Roof or O for Observation Deck.
• The ground floor may be G for Ground, M for Main, L for Lobby, or simply 1 (if it is also the first floor) or 0 (if not). As an aid to the visually impaired, there is often an embossed * beside the button.
• Below the ground floor is commonly B for Basement or P for Parking, sometimes L or LL for Lower Level.
• Below the basement may be SB for Sub-Basement. Numbered levels below ground, such as B1 or P1, are also common; the numbers may run either way, but B2 is usually below B1. Negative numbers (-1 for the first floor below ground, then -2, etc.) are also used, especially when the ground floor is numbered 0.
• Some buildings are just idiosyncratic; at one hotel in Toronto, the first six floors are labeled A, M, MM, C, H, and 1 (for Arcade, Main, Main Mezzanine, Convention, Health Club, and 1st floor).
• Floor designations sometimes vary between different banks of elevators in a building (due to its layout), or even between buttons and indicators in the same elevator (due to careless installation).
• Some elevators, especially in buildings with complex floor plans, have both front and rear doors that can open at the same floor; a second button with R appended to the floor abbreviation (e.g. GR or 2R) then requests a stop there with the rear door opening.

The convention that higher floors have their buttons placed higher may help resolve ambiguities, but many elevators have enough buttons that they are grouped in rows of two or even three.

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In order to comply with laws regarding handicapped access, such as the Americans with Disabilities Act (ADA), a secondary button panel may be installed which is located at a height that can be reached by a person in a wheelchair. In this case the buttons may be arranged in a horizontal fashion.

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On the elevator's position indicator, you may see the letters EZ. This is used to represent an Express Zone which is a long section of travel where the elevator makes no stops. Typically these are found in elevators that serve the upper reaches of tall buildings, thus bypassing several of the lower floors on the way.

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The elevator algorithm

The simple algorithm by which a single elevator can decide where to stop is:

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• Continue travelling in the same direction while there are remaining requests in that same direction.
• If there are no further requests in that direction, then stop and become idle, or change direction if there are requests in the opposite direction.

The elevator algorithm has found an application in computer operating systems as an algorithm for scheduling hard disk requests.

Related Topics:
Operating system - Hard disk

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Modern elevators use more complex heuristic algorithms to decide which request to service next.

Related Topics:
Modern - Heuristic algorithms

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Computer dispatched

Efficiencies of multiple elevators installed in an office building may increase if a central dispatcher is used to group passengers going to the same floor to the same elevator. In buildings with these computer-dispatched elevator system, passengers key in their destination floor in a central dispatch panel located at the building lobby. The dispatch panel will then tell the passenger which elevator to use. Inside the elevator there is no call button to push (or the buttons are there but they cannot be pushed, they only indicate stopping floors). Manufacturers of such systems claim that average travelling time can be reduced by up to 30%. Sometimes, however, 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 late comers may find the elevator they're assigned to is already full.

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Special operating modes

Up peak

During Up Peak mode, 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 maximim use of the available elevator system capacity.

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The commencement of Up Peak may be triggered by a time clock, by the departure of a certain number of fully loaded cars leaving the lobby within a given time period, or by a switch manuallly operated by a building attendant.

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Down peak

During Down Peak mode, elevator cars in a group are sent away from the lobby towards the highest floor served, after which they commence running down the floors in response to hall calls placed by passengers wishing to leave the building. This allows the elevator system to provide maximum passenger handling capacity for people leaving the building.

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The commencement of Down peak may be triggered by a time clock, by the arrival of a certain number of fully loaded cars at the lobby within a given time period, or by a switch manually operated by a building attendant.

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Sabbath service

In areas with large populations of observant Jews, one may find a "Sabbath Elevator". In this mode, an elevator will stop automatically at every floor, allowing people to step on and off without having to press any buttons. Regenerative braking is also disabled if it is normally used, shunting energy collected from downward travel, and thus the gravitational potential energy of passengers, into a resistor network. This prevents violation of the Sabbath prohibition against doing useful work.

Related Topics:
Jew - Regenerative braking - Potential energy - Resistor - Sabbath - Work

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Independent service

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 centralised control panel. When an elevator is placed on independent service, it will no longer respond to hall calls. (In a bank of elevators, traffic would be rerouted to the other elevators, while in a single elevator, the hall buttons will be 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.

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