Editing 40d:Lever

{{quality|Exceptional|13:32, 6 July 2011 (UTC)}}{{av}}
A '''lever''' is a [[mechanism]] that has been constructed on a floor tile. Once in place, it can be linked to one or more other devices such as [[door]]s, [[bridge]]s or [[support]]s, permitting you to control these other devices by ordering the lever pulled through its {{k|q}} menu.  

Levers do not block movement.  Levers are counted as furniture for [[created wealth]] of a fortress.

A lever can be [[Workshop#Profiles|limited]] to who can pull it, similar to a workshop, in the {{k|q}} {{k|P}}rofile for that lever.  (This can be handy for a variety of special purposes.)

[[Pressure plate]]s are like levers, but are activated automatically by [[creature]]s stepping on them, or by fluids reaching a certain (player-selected) depth.  

Either a '''lever''' or a [[pressure plate]], once linked to one or more devices ([[door]]s, [[trap]]s, or whatever), can act as a '''trigger''', an activation mechanism for that secondary system.  The two are activated differently, but the connected system is activated just the same.  One system can have more than one trigger linked to it, and one trigger can be linked to more than one system. 

''For a basic overview of how the different machine parts work and work together, see [[machinery]].''

==Placing a lever==
If you have a spare mechanism, you can designate the new lever job via the  "{{k|b}}uild {{k|T}}rap {{k|l}}ever" keys, and can use {{k|x}} to choose which specific mechanism to use.  Mechanism [[quality]] has no known effect on the performance of the lever.  Low-quality mechanisms work fine, but since they are counted as furniture, high quality mechanisms give more [[created wealth]].

==Linking==

Once a mechanism has been placed as a lever, it then requires a pair of [[mechanism]]s to link that lever to any object, regardless of distance or size, and [[quality]] of the mechanism makes no reported difference.  This is done by giving the lever the appropriate job order via {{k|q}}(similar to any workshop), selecting what sort of object you want the lever linked to*, and then using the {{k|-}} and {{k|+}} keys to scroll through the available examples of those and selecting the one you want.  The list is chronological, with the last object finished listed last, and the map will re-center on the exact object as you scroll.

:''(* [[bridge]], [[cage]], [[chain]], [[door]], [[floodgate]], [[hatch]], [[grate|wall grate]], [[grate|floor grate]], [[bars|vertical bars]], [[bars|floor bars]], [[support]], [[spike]], or [[gear assembly]].)

By default you can choose the specific mechanisms you wish to use, from a list of all you have created (and are not forbidden or isolated by [[path]]) - your first selection will be attached to the item/barrier in question (the door, floodgate, cage, whatever), and the second selection will be linked at the lever end (the order is important when dealing with [[magma]]).

A lever can be connected to any number of objects at the same time, but, as each linking is a [[job]] designated at that lever, only one linking job will be tasked at any one time - after that job is finished, the next will begin.  (That is, if you want one lever connected to 101 different doors, hatches, cages, bridges and supports, you can do that, but those jobs will not occur ''simultaneously''.)  Up to 10 linking jobs can be queued up at any one time on one lever, the same as with jobs at any workshop.

Once a link is completed (not queued), the target will no longer appear in the lever's target list. However, if you queue the same linkage twice then both tasks will be performed. This has no effect other than to use up more mechanisms.

Once linked, a trigger can only be de-linked by deconstructing the trigger itself or the target. By doing so you will recover the linking mechanism used on that side. To get both back you will need to deconstruct both the trigger and the target.  Deconstructing a linked object has no effect on other objects linked to the same lever; deconstructing a lever unlinks all objects linked to it.  If you wish to relink an object to the same lever, you must use two new mechanisms - you cannot "re-use" the mechanism still in the lever without deconstructing that, too, and starting over entirely.

==Activating levers==
A lever is activated (or "pulled") through its {{k|q}} menu with via the "{{k|a}}dd new task {{k|P}}ull" keys, which establishes a new [[job]] that then needs to be filled.  An idle dwarf will then come to pull the lever - no labor need be designated for this task, so ''any'' adult civilian dwarf might volunteer, and from ''anywhere'' on the map that has a [[path]] to that lever at the time, though in most cases the nearest dwarf will be chosen. 

[[Tantrum]]ing dwarves have also been reported to pull levers at random, leading to all kinds of [[fun]].  

Note that once the actual ''lever'' is pulled, any attached objects may take more time to respond - see below.

====Specific Response Levers====
Some lever systems are intentionally designed to be pulled only by specific dwarves. By limiting which dwarf/dwarves can respond to an order to "{{k|P}}ull Lever" (via that lever's [[workshop profile]]), you can control who responds, which specific dwarf pulls that lever.  This means you can largely control who will be standing "right there" when that lever activates... whatever.

This can be used for...

:* Limiting general lever pulling to [[hauler]]s and other relatively useless dwarves.
:* Retiring unwanted [[noble]]s or other dwarves - see [[unfortunate accident]].
:* Locking a dwarf behind a door - for instance, [[Bauxite#Bauxite Management|locking a mason or mechanic in with bauxite]] to force them, and only them, to work with it.
:* Sealing an otherwise relatively useless dwarf in a lever [[control room]].
:* Choosing a sacrificial dwarf for a suicide lever pulling mission.

==On/Off vs Open/Close==
Levers normally have an "on" and an "off" state, seen as whether the small tag at the top of the lever is to the left ("off" state) or the right ("on" state).  Upon being pulled, the state of the lever changes, and everything they're connected to updates to the ''corresponding'' state of that lever, and does not just ''change'' states ("toggle").  This becomes important if you have several levers attached to the same device, or one trigger attached to several systems. 
:Example: 2 levers (both in "off" position) are connected to a drawbridge. After pulling the first lever, the bridge will lift. Pulling the second lever tells the bridge to "open", which it already has done - no visible effect. When it is pulled a second time it will let the bridge down. This in turn requires the ''first'' lever (still in "open/lift" position) to be pulled twice to trigger a change (lift again), and so on.

"On" and "off" state is fixed and dependent on the lever, not the object that lever is linked to:

* "dash to the right" ( '''ó''' ) is '''on'''
* "dash to the left" ( '''ò''' ) is '''off'''

Note, however, that gear assemblies are ''the sole exception'' to this: Instead of On/Off triggers, they indeed '''do''' toggle.

Several devices, such as [[floodgate]]s and [[bridge]]s, have a delayed response to all incoming signals, and will not respond to subsequent signals until the first has taken effect.  For instance, if you pull a lever attached to a floodgate on then off in rapid succession, the floodgate will only respond to the first signal, independent of the position the lever rests in eventually.

==On/Off states==
Objects that can be controlled by levers include:

===== Multiple Uses =====

A "step" is not a step that a dwarf makes, and not based on [[FPS]].  It's one "step" that the game advances.  When paused (via {{k|spacebar}} ), you can manually advance the game "1 step" by hitting the period ( {{k|.}} ) key.

* [[Bridge]] – Activates 100 steps after being triggered
** '''On:''' Turns the bridge into either a raised drawbridge, or a retracted bridge, depending on which option was chosen when the bridge was constructed. 
** '''Off:''' Returns the bridge to normal.

* [[Door]] – Activates instantly. Note that once you connect a door, it is either completely open or sealed shut. There is no "''closed, but can be opened by a dwarf''" state anymore.
** '''On:''' Opens the door. 
** '''Off:''' Closes the door. 

* [[Floodgate]] –  Activates 100 steps after being triggered. 
** '''On:''' Opens the floodgate. 
** '''Off:''' Closes the floodgate.

* [[Floor hatch]] – Activates instantly.  Note that, like doors, once you connect a hatch, it is either completely open or sealed shut.
** '''On:''' Opens the hatch.
** '''Off:''' Closes the hatch.

* [[Grate]] – Activates 100 steps after being triggered. When it is open, it just disappears. Liquids go through it just the same, but it cannot be walked on anymore. Anybody on it will fall.
** '''On:''' Opens the grate. 
** '''Off:''' Closes the grate. 

* [[Bars]] – Activates 100 steps after being triggered. When it is open, it just disappears. Liquids go through it just the same, but it cannot be walked on anymore. Anybody on it will fall.
** '''On:''' Opens the bars. 
** '''Off:''' Closes the bars.

* [[Trap|Upright Spear/Spikes]] – Activates 40 steps after being triggered.
** '''On:''' Retracts spears/spikes.
** '''Off:''' Extends spears/spikes.

* [[Gear assembly]] – When it is disengaged, no power goes through it and anything that is being kept up by its presence (like a [[windmill]] right on top of it) falls down.
** '''On:''' Toggles gear state.
** '''Off:''' Toggles gear state.

===== One-Shot =====

These items, when activated, deconstruct, and/or cannot be triggered again until re-linked.

* [[Cage]] &ndash; Deconstructs the cage and releases all of its contents. The cage and its attached mechanism will be left on the floor nearby; you recover the [[mechanism]] used on the cage but you do not recover the mechanism used in the lever. For this you need to deconstruct the lever too.

* [[Restraint]] &ndash; Deconstructs the [[Restraint|chain/rope]] and releases whatever creature it held. The restraint's mechanism will be left on the floor nearby, and the restraint itself will remain attached to the creature's neck; again, you recover the [[mechanism]] used on the restraint but you do not recover the mechanism used in the lever. For this you need to deconstruct the lever too.
* [[Support]] &ndash; Deconstructs the support, ideally without a dwarf next to it. Most commonly used to cause controlled [[cave-in]]s.

==Control Room==
Some players prefer to create a "control room" and lock a dwarf in when they expect to need quick response to their levers, to avoid long delays.  A control room is an area where important levers are located.  It often has doors/hatches on all entrances, so a dwarf (or more than one) can be locked inside to guarantee that one nearby dwarf will be idle who can pull a lever at a moment's notice, rather than wait for the first idle dwarf to respond, who might be far across the map. This can be critical with some of the more complex [[Trap design|trap designs]].  For longer sieges, a small personal stockpile of booze and food is critical, or an "airlock" that can be (re)stocked for prolonged situations.

Some control rooms have all doors linked to a single lever, which is the first one pulled - this seals in the first volunteer to respond, although {{k|A}}ctivating a specific recruit and stationing them and then manually locking them in the control room is sometimes faster.  Double doors, one set manual, and one set linked, allow for manual sealing of the room in either manner.  (It's advised to have a backup lever somewhere to open the linked doors in case of accidents.)

Advanced players do not trust doors alone to protect their control room, as some fortress invaders are [[building destroyer]]s, and can deconstruct any door or drawbridge they come across.

Because control rooms often contain levers linked to most every important system in the fortress, it's critical to guard it against troublemakers like [[gremlin]]s and [[tantrum]]ing dwarves.  Having wardogs or other attack animals chained at all entrances is a good start, and military stationed nearby is popular as well.

Because of the crowded nature of a control room, it's particularly important to [[label]] your levers, and/or organize them for positive identification as to function.  Returning to a game after a week and not remembering which "red" lever releases the magma or shuts the main gate is too much [[fun]] for some players.

==Labeling==
There is no way to determine what levers operate what objects except by pulling them and seeing what happens.<sup>*</sup>  Because of this, it can be critical to, somehow, keep track of what lever does what and where (''especially'' in a control room!).  [[Note|Label]]ing each individual lever is (possibly) the most foolproof.  Some players (additionally) use architecture or color coding to help label their levers, either placing them near the objects they activate, or in small bays organized in groups (even within a control room), and/or making the mechanism (and linked objects) out of a [[The Non-Dwarf's Guide to Rock|particular colored]] stone, or likewise coloring the nearby wall or floor, or even constructing a letter or symbol in a floor mosaic - whatever works, so long as it ''does'' work.

:<sup>(*): Not exactly true. You can attempt to link the lever to a new object. Anything already linked to that lever will not show up in the list, as an existing link cannot be duplicated. So you could, in theory, look through the entire list; any item which doesn't appear in that list is linked. However, this process of elimination becomes a very daunting prospect with, say, doors.</sup>

==Locked vs. shut via link==

Note that while a [[thief]] can bypass a "locked" [[door]] or [[hatch]], any barrier linked to a mechanism and in the "closed" position is impassable to any creature.  However, some creatures have the [[building destroyer]] tag, and can deconstruct the barrier entirely if they can reach it.

== Computing ==

Elaborate combinations of levers (or pressure plates) and other objects can be used to create mechanical systems that can perform various forms of [[computing]].


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