Interestingly, the old two-aspect station starter
and single-aspect inner home at Ongar are still extant ...

What's a single-aspect signal?

A signal with only one aspect.

Sigh. Okay. What *use* is a single-aspect signal?
--
Mark Brader ...the scariest words of the afternoon:
Toronto "Hey, don't worry, I've read all about
doing this sort of thing!" -- Vernor Vinge