User:Khearn/Mechanics101

This is a collection of basic stuff one needs to know about mechanical stuff.

Open/Close signals

Many people seem to assume that levers and pressure plates send a toggle signal, that causes a bridge/door/whatever to simply change state. This is wrong, they send either an "on" or an "off", and the target responds, depending on what it is. It's a trivial difference if only one lever is connected to one bridge, since pulling the lever twice will get them synced up and henceforth pulls do indeed simply toggle the bridge (as long as they don't come too fast).

But if you connect two levers to the same bridge, things get more complicated. Pulling lever 1 may raise the bridge, but then pulling lever 2 doesn't seem to do anything, because it sends an on to the bridge that was already raised. At this point, but levers are in the on position, and pulling either one will lower the bridge.

Note that you can tell what state a lever is in by it's character (assuming you use ASCII - but most tilesets make it fairly obvious). If it's an ó then it is in the on position (and will send an off if pulled), and if it's an ò it is in the off position.

Here's a summary of the various things you can link a lever to, what they do when they get an on or off, and the delays that might be involved.

Item	On		Off
	Action	Delay	Action	Delay
Bridge	Raises or retracts	100 ticks	Lowers or extends	100 ticks
Door	Opens	Immediately	Closes	Immediately
Floodgate	Opens	100 ticks	Closes	100 ticks
Floor Hatch	Opens	Immediately	Closes	Immediately
Grate (vert or horiz)	Opens	100 ticks	Closes	100 ticks
Bars	Opens	100 ticks	Closes	100 ticks
Upright Spears/Spikes	Retracts	40 ticks	Extends	40 ticks
Gear assembly	Toggles	Immediately	Toggles	Immediately
Track Stop	Disables	Immediately	Enables	Immediately
Cage	Opens/deconstructs the cage	Immediately	N/A	N/A
Rope/Chain	Releases/Deconstructs	Immediately	N/A	N/A
Support	Deconstructs	Immediately	N/A	N/A

Pressure plates send an on signal immediately when their criteria is met, and an off signal 99 ticks later.

Note that some things may respond to a signal a tick later, depending on the order in which things were built. See Pressure Plate#Build order for more details.