Re: [Jmri-developers] forwarded, Attn David Duchamp: Automatic automated train operations

[Ken C. <kca...@st...>]

My thoughts about the prototypical clearing of opposing signals in APB.

I do the simple flag for if the track is set for a direction and set all
the opposing to red until the whole path clears right now. But here are
my ideas of how I could do it otherwise.

Initially we'd still set all the opposing signals to red. But instead
each signal would have a direction flag of its own. After a train
passes, it would clear. I'd still have the flag for the direction of the
whole route however or rather that's the direction flag of the opposing
head block signal. That head block signal would not come out of hold
until the whole section of APB is clear. In the mean time each of the
other opposing signals would return to normal ABS after the first train
passed.

Where this is handy is for the first train to know if there is somebody
following as the opposing would change according to normal ABS behavior.
Handy to know if you were broke down or doing switching and needed the
reminder that somebody wanted to come along after you. Which if TT&TO
and you knew the following train was superior to you, you'd want to know
it finally was catching up and that at the siding ahead you may have to
double up if also opposing traffic was there.

So the part I don't have right now is having the separate flags for each
intermediate signal and the logic to clear that after the first train
goes by.

Some my understanding of APB comes from an article series in MR
published Nov 1991 by Jay Boggess. The article was on making a set of
logic cards to do it all in hardware but the first installment covers
all the whats, whys and hows. It introduced ideas like 'Overlap
protection', 'Double Approach', and 'Overlap Nullification' and how they
impact how the trains can and can't pack into the spaces.

Since this thread is gathering a lot of details about where the current
SSL doesn't go and things that might help automated trains I figured I'd
stick it into the messages.


-ken cameron
Syracuse Model Railroad Club http://www.SyracuseModelRr.org/
CNY Model Railroad Club http://www.cnymrrc.com/
mailto: kca...@st...
_Sept 11-14 2008 NMRA-NER Convention, Syracuse NY,
http://empirejunction.org/home.html