Lesson 4 - Handling Stepping Up Aspects (Click on thumbnails to expand)
(toolbar reminder) 
Lesson 3 left us with a working panel but with the home signals staying at yellow, even when the starter was cleared to green.
Stepping up is when a signal clears to a better aspect, this may be from red to yellow or red to green or yellow to green or some of the other permutations
The problem we need to resolve is the distant s10, will stay at yellow if the home signal s9 is triggered straight to green, so to solve this we add an extra trigger into fmClears10 - and change the condition, in the checked elements, if necessary from an "and" to the "or" - this extra trigger is s9 being green (Fig 1)
Fig 1
For this lesson we are going to add two new flagmen to step up (change from yellow to green) the home signals when required and fix a "problem" on the distant signals (deliberately left in)
We add the two new flagmen, one for each home signal and set their properties as follows - dealing with the down only - the flagman is triggered when the starter signal s8 clears (fig 2) , it needs to set the home signal s9 to green (fig 3).
 Fig 2 |  Fig 3 |
Download a zip file containing the working files for this stage.
When we test the down signals we see that by clearing the home route and then the starter route all our signals should go to green !! (Fig 4)- Yippee ? - sadly not quite.
Fig 4
When we clear just signal s8, signal s9 clears too and to make it worse signal 10 also clears (Fig 5) - darn !
Fig 5
Additionally if the starter is cleared first then the home signal resets to yellow (Fig 6) - double darn !
Fig 6
To solve both of the problems needs a little bit more work with our new home flagman - we need the flagman to be additionally triggered if we clear the s9 signal route, so we add this in as an additional "or" trigger (Fig 7)
Fig 7
To solve both of the problems needs a little bit more work with our new home flagman - we need the flagman to be additionally triggered if we clear the s9 signal route, so we add this in as an additional "or" trigger - but this introduces a temporary problem whereby the home will clear if only the starter is cleared (Fig 8)
Fig 8
To solve this problem we add an addition condition on the home signal flagman such that it only applies if the route from s9 to s8 is set (Fig 9)
Fig 9
To complete the panel to the end of lesson stage we add the same controls onto the up home flagman and (hopefully!) end up with a fully working panel (Fig 10) - or is it ?
Fig 10
Download a zip file containing the working files for this stage.
If you would like to correspond on this matter then please use the contact us page
Last updated : December 10, 2007 22:42