Rich: I think that Swav was talking about the location of the light aspects within a signal head. Probably a Type D with three aspects, and generally, but not always, the green aspect was on top. If I understand your comment, you are talking about multiple signal heads on one mast, am I right?
Of course exceptions are the rule, and I've seen signal heads with only two aspects, say amber and red, in which case the upper aspect, normally green, was simply blank.
As to the number of signal heads on one mast, I recall in Chicago that the Northwestern, which primarily used signal bridges on multiple track lines, had one of these massive bridges with a number of masts, one for each track beneath the bridge, and on each mast there were three and four signal heads. Most of the indications were red at any one time.
Paul Fischer
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