Does an N&W "Interlocking Book" Exist ?

[NW Mailing List]

I second Abe's request for a copy of a N&W Interlocking Book.  I am writing a series of articles on the history of N&W signaling for THE ARROW and diagrams from such a book would add immensely to my presentation.

Glenn Fisher
Myerstown  PA



From: NW Mailing List 
Sent: Friday, October 29, 2010 4:07 PM
To: nw-mailing-list at nwhs.org 
Subject: Does an N&W "Interlocking Book" Exist ?


Was there ever an "Interlocking Book" issued by the N&W Signal Department? 


Larger railroads usually made these up from blueprints (the longer prints being folded accordion style,) and held together by brass brads. Because they were hand-assembled, a limited number of copies were made.  Each Signal Supervisor had one, and the various Division and system offices had copies for reference.  The ones I have from other roads were organized by Division (a book listing the interlockings of one Division only,) and the books appear to have been reissued about every five years.  


The content of the Interlocking Book was rather technical, but it is invaluable to the student of history.  A typical page from such a book would show a track diagram of the interlocking, the number of each switch, crossover and lock, the number of each home and automatic signal, the aspects each signal was capable of displaying, the distance in footage from the distant signals to the home signals,  the type of interlocking machine in use and date of installation, a designation of the model number of the switch machines or valves employed, and sometimes the locations of the insulated joints, the track circuit numbers, and the battery polarity applied to the rails of each track circuit.  Usually a good bit of history was also shown on the sheet, such as date the facility was constructed and its exterior dimensions, any rebuilt dates, and the dates for the application of route locking and time locking, neutral and polar switch correspondence protection, and any other significant upgrades or changes to the plant.  If the interlocking was in coded track territory, the location of the code change points was sometimes shown.  And, of course, a history of revisions made to the blueprint would be shown.


Does any such document exist in the Archives, or is one known to exist in a private collection?  If so, this would be a great "reprint" opportunity for the N&W Historical Society.


-- Abram Burnett






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