40d:Lever

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 doors, bridges or supports, permitting you to remotely control these other devices through the lever's q menu.

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

Pressure plates are like levers, but are activated automatically by creatures stepping on it, or by fluids reaching a certain (player-selected) depth.

Either a lever or a pressure plate, once linked to one or more devices (doors, traps, 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.

Placing a lever

If you have a spare mechanism, you can designate the new lever job via the "build Trap lever" keys, and can use 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 mechanisms 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 q(similar to any workshop), selecting what sort of object you want the lever linked to*, and then using the - and + keys to scroll thru 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, wall grate, floor grate, vertical 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 must be deconstructed to de-link it from a system*; this also unlinks all other connected systems to that trigger, but has no effect on other triggers linked to the same system(s).

(* Or if the other end is deconstructed, the door, hatch, column, bridge or whatever, that un-links the trigger as well, but any other system remains linked.)

Activating levers

A lever is activated (or "pulled") through its q menu with via the "add new task Pull" 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 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.

Tantruming 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.

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 floodgates and bridges, 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

(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.)

• 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 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.

• 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.

• Upright Spear/Spikes
  • 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 – 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 until you deconstruct the lever itself.
• Restraint – Deconstructs the 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 until deconstructing the lever itself.
• Support – Deconstructs the support, ideally without a dwarf next to it. Most commonly used to cause controlled cave-ins. The support's building material and its attached mechanism can both be recovered (unless they happen to get destroyed in said cave-in).

Control Room

Some player 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 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 Activating 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 destroyers, 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 gremlins and tantruming 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.^* Because of this, it can be critical to, somehow, keep track of what lever does what and where (especially in a control room!). Labeling 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 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.

^{(*): 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.}

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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