In article , Mark Brader
writes
Interestingly, the old two-aspect station starter
and single-aspect inner home at Ongar are still extant ...
What's a single-aspect signal?

* Fixed distant.
* Repeater for an approach-released signal.
* Fixed red where trains can't proceed any further in this direction.
* Some North American lines use a single aspect blue signal as part of
a gantry-full (or a set of signals all to the side of the line) to
mean "no signal applies to this track".

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Clive D.W. Feather | Home:
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