Layout and Signal Description

MLS Layout with Labeled Turnouts (blue) and Blocks (orange)

One difficulty with making layout control software reusable is providing a generic description of the layout and what aspects to control. while this can no doubt be done for simple layouts, it becomes more difficult with bigger or complex layouts, such as the one above. In the above diagram, turnouts are identified in blue, blocks in orange and signals locations in read.

Layout Description

The layout is further illustrated in auto-generated schematic diagram below using the description at right. In the layout description, turnout switches are described with a "sw" description which provides a numeric label, indicates whether the diverging tracks face east or west, that the diverging rail is to the right or left and an optional location.

The "con" descriptions indicate how switches are connected and optionally identifies a block for the trackage connecting them. The switch to the west must be on the left. The switch connections are to the points, "p", the normal route, "n" or the diverging route currently identified as right, "R", or left, "L".

Block assignments are still somewhat ambiguous because either the blocks are very short when there is little trackage between the turnouts or the trackage may be in common with several blocks usually more easily identified as the longer blocks between the turnouts and the next signal.

Signal Descriptions

In addition to a description of the layout are descriptions of the signals. Each signal may protect one or more different routes depending on the number of turnout following it.

Of course a signal indicates STOP if the block for the aligned route is occupied. But if not occupied, the are several possible indications

And when the next signal indicates anything other than CLEAR, the following indications are possible

Each route is identified by signal number, block, signal indication when clear, next signal number for that route, the signal indication when the next signal not clear and one or more switches and position defining a route. The entries below lack block numbers and signal indications. But the number of entries suggests how many signals indications need to be considered.