Idle signal aspects

NW Mailing List nw-mailing-list at
Thu Nov 17 10:13:40 EST 2016


I think what you are asking about is a signal's idle aspect which is 
displayed in the absence of traffic, lined routes and faults. Controlled 
signals displayed Stop and Stay and automatic signals displayed Clear, 
except for Approach aspects in advance of a Stop and Stay. An exception 
to this in double-track territory was that the reverse main automatics 
all displayed Stop and Proceed, but only in some sections. Lacking an 
apparent operational reason, this inconsistency may be just different 
versions of installed logic. (Abram?) In addition to signal system 
blueprints, early CTC panels featured a graphic symbol for each signal 
that, in part, indicated the idle aspect.

Grant Carpenter

On 11/16/2016 6:26 AM, NW Mailing List wrote:
> What was the "default" aspect for N&W CPLs in the absence of traffic?  
> Since they ostensibly simply indicate block occupancy, it would seem 
> that if there were no trains, all intermediates would be showing 
> CLEAR, but somehow this doesn't "feel" right to me.  If I had had the 
> foresight to go out along the line on a Christmas day in the 70's and 
> examine the state of intermediate signals, would I have seen all green?
> adthanksvance
> Jim Cochran

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