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Control Panel Not Included in Train Communicator

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KGround
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Iron
Just curious ...
KGround   10/10/2012 5:17:49 PM
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What happens when a train and the maintenance person happen to pick the same relay (issue the same command) at nearly the same time ?  Since this would presumably be a physical impossibility without the pushbuttons (unlikely two trains would be in range of the same inductive  loop at the same time), my guess is that the control program might well get confused by this and run amok.  

I am assuming that the control program has provisions for dealing with simultaneous requests on multiple inputs, but maybe not.  Again, the nature of the physical plant or the way the trains are operated may mean that this never happens in the absence of the pushbuttons, and thus the possibility of multiple commands that is presented by the added buttons may also have been not coverred in the programs.

RailroadGeek
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Iron
Re: Just curious ...
RailroadGeek   10/13/2012 2:30:51 AM
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First, there is a switch in the common lead of the panel so that automatic operation and the local control panel are not enabled at the same time.

Secondly, the PLC also processes signal/switch requests on a "first come/first serve" basis and it has a built in provision (all inputs are checked with multiple "Exclusive OR" gates) to reject coincidental and conflicting requests from any single loop antenna.

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