Home
»
Trains Magazine
»
Forums
»
General Discussion
»
"I fight authority, authority always wins."

Edit post

Edit your reply below.

Post Body
Enter your post below.
[quote user="Murphy Siding"][quote user="edblysard"] Yes...they do. See the photo in the link I posted above. The Stop sign protects the PTRA main from the old SP cut across from their Clinton Sub. The sign is normaly displayed against the SP....when they want to cross our main, they pull up, stop, look, and if no traffic, they swing the gates open locking them against the PTRA...when they are through servicing the small plant in the background, or if they are just crossing, they line the gates back against the SP main. They was a manual interlocker about a mile west, (left) of this shot...it had a four way stop sign. Just like on a public street, you pulled up, stopped, and if no opposing traffic, you flaged through. It has been replaced by four red over lunar signal heads and a circut, which is a pain, it screws up every time it rains! [/quote]      Is a manual interlock something like I saw in a book about local railroad history-the photo showed a switchman "winding the clock at the interlock"(?).  This was at a diamond where CNW trains infrequently  crossed a regularly used BN line.[/quote] No.  A manual interlocking is one controlled by a human being.  An automatic interlocking operates without human intervention.  The human being that controls the manual interlocking can be located in a tower at the interlocking, 20 miles away running several interlockings (PRR and B&O had lots of these), and 2000 miles away in a dispatching office.  Manual interlockings are essentially indistinguishable from CTC in practice, rules, and technology.  Another way of looking at it is that manual interlockings require a human being to decide who goes first.  Automatic interlockings run on a first-come, first-serve basis.  Automatic interlockings generally have a manual override in the field, which is what you observed in the photo you describe.  The basic difference between an interlocking and a crossing at grade protected by stop signs is that the interlocking uses signal indications to govern routes and has track circuits to detect the occupancy of a train inside its plant, and sets the signals accordingly.  Of course in both cases a trainman or engineman can disregard the signal or the stop sign or the presence of another train and proceed anyway.  Interlockings prevent the control operator from lining conflicting routes.  The term "interlocking" derives from the fact that the first interlocking machines were mechanical and used interlocking fingers inside the machine to lock-out hand levers (armstrong levers) that would set up conflicting routes, until the selected route was cleared.  Mechanical interlockings were replaced with relay logic and in turn with digital logic. S. Hadid
Tags (Optional)
Tags are keywords that get attached to your post. They are used to categorize your submission and make it easier to search for. To add tags to your post type a tag into the box below and click the "Add Tag" button.
Add Tag