JMRI: Warrants Help
Author: Karl Johan Lisby
Keywords: JMRI Fast Reacting Warrant Help

# Fast Reacting Warrants

This type of Warrant does not follow the standard Prototypical Warrant rules, but instead reacts to signals with an immediate speed change upon entering their approach block.
The throttle settings are a fixed proportion of the Aspect Speed Names in Warrant Preferences. It is specially adapted for small layouts with short blocks.
Apart from standard and Fast Reacting Warrants, a third type is eNtry-eXit or NX Warrants

A number of nice features in standard Warrants have been sacrificed in Fast Reacting Warrants for the sake of speedy and reliable control of small layouts. This includes disabling of speed ramping and the ability to control bells, whistles and light when the train enters a block.

Likewise a few features available in Fast Reacting Warrants that are not present in standard Warrants.

First and foremost Fast Reacting Warrants are controlled by signals (hence their technical name Signal Controlled (SC) Warrants). This obviously requires that you have defined signals - at least virtual signals - on your layout and that you have added those signals to your OPortals. If you have done that, the Fast Reacting Warrant will constantly "look" at the next signal along its route and adapt the speed of the train to the Aspect shown by that signal. This speed adaptation happens promptly and no matter how often the Aspect changes. Thereby the train will stop even within short blocks.

Note: If you have slow moving turnouts on your layout, you have to protect each turnout with a signal. Otherwise a train might run through the turnout while it moves.

An additional feature of Fast Reacting Warrants is that it is possible to define a number of milliseconds that the train shall continue with low speed after it has entered the destination block. This is in part a substitute for the very flexible way standard Warrants are able to execute throttle commands. But it is also a quite reliable way to make the train stop at the same location every time.

One more requirement to your layout: Fast Reacting Warrants do not handle "dark" Blocks. I.e. all those Blocks you use in the route for a Fast Reacting Warrant must be equipped with an occupancy sensor. I.e. the Warrant must at all times have at least one sensor active (and thereby an OBlock occupied) while the Fast Reacting Warrant is running a train.

## Comparison between Warrant types

Feature | Standard | Fast Reacting (SC) | Entry Exit (NX)
Ramps speed up and down | yes | no | yes
Executes throttle commands as recorded | yes | no | no
Can be stored / is permanent | yes | yes | no
Can be converted to another type | to SC | to standard | to standard or SC
Recording of throttle commands | yes | no | no
Calculation of throttle commands | no | yes - while running | yes - during creation

## Creating and running a Fast Reacting Warrant

A Fast Reacting Warrant is created and used in the same way as standard Prototypical Warrants. You may even switch back and forth between a Fast Reacting Warrant and a standard Warrant.

Simply change the Warrant type in the Warrant Editor.