JMRI: Turnout Feedback

Model railroaders want different things when it comes to knowing the status of the turnouts on their layout. Some are quite happy to say "I told it to move, that's good enough for me". These people don't worry about whether a turnout on their layout actually moved when they told it to. Those people can just ignore this page, and leave the JMRI settings at their default.

But some modelers want to have better information about the status of the turnouts on their layout, and so use some form of "feedback" to indicate turnout position. This could be as complicated as two microswitches, adjusted to only close when the turnout is properly seated in either position. Or it could be something simpler.

In the code, Turnout objects actually know about two different states: "Commanded" state and "Known" state. The commanded state is "This is what was asked for last". The known state is "This is what's actually correct on the layout as far as I know".

Built into both LocoNet and XPressNet are limited abilities to monitor what is happening on their networks and adapt to messages about Turnout state changes. All the other protocols normally use a "you told it to change, so it did" logic. In other words, when something in the code (the Turnout Tool or a script) commands a state change from closed to thrown, the default is for both both the commanded state and the known state to change to "thrown".

But it is also possible to control this in more detail if you have wired your layout to allow it.

The whole question of turnout feedback is then "How do we configure the program to understand the known state properly, given my layout hardware?"

If you go to the "Turnout Table" tool, you'll find it has four columns associated with feedback:

"Feedback": This is the "known state". You can't change it, but this column will show you what the program thinks it is.
"Mode": This is the feedback method used by this turnout. (You can change it for each turnout individually, but note the change doesn't take effect until you click somewhere else, and you might need to add some sensor names in the next column(s))
"Sensor 1", "Sensor 2": These define the sensors needed by certain types of feedback. You can type a sensor number, system name or user name here; the program will change it to the system name that it needs.

Available feedback modes are:

DIRECT: The default in many cases, and also the original behavior of the program. When something tells the turnout to change, it's just immediately assumed that it actually did it.
ONESENSOR: The turnout watches the sensor defined by the "Sensor 1" column, which is probably hooked to a microswitch on the turnout or similar. When the sensor is Active, the turnout is known to be in the "Thrown" position. When it's Inactive, the turnout is known to be in the "Closed" position.
TWOSENSOR: The turnout watches two sensors defined by the "Sensor 1" and "Sensor 2" columns, which are probably hooked to microswitches at either end of the turnout's throw bar. When Sensor 1 is active, the turnout is known to be thrown. When Sensor 2 is active, the turnout is known to be closed (normal).
MONITORING: Default for LocoNet turnouts (and probably XpressNet soon), this means the network is monitored for messages about the status of the turnout. This mode is only available for certain protocols, i.e. some protocols can't do the monitoring properly, and don't have this choice.
INDIRECT: Currently only available for LocoNet turnouts, this informs the program that the turnout is being driven by a Digitrax DS54 with a microswitch attached to the switch lead. For more information, see the DS54 page.
EXACT: Currently only available for LocoNet turnouts, this informs the program that the turnout is being driven by a Digitrax DS54 with two microswitches attached to the switch and aux leads. For more information, see the DS54 page.

Most people will (and probably should!!!) stick with the default feedback type that the software selects for them.

Right now, the only people who should probably run out and try this are those who have their Digitrax DS54 devices set up to trigger from a local input, and to send sensor messages when that happens. in that case, switching to "ONESENSOR" or "TWOSENSOR" feedback will make everything work properly. (DON'T FORGET TO SAVE THE CONFIGURATION!)