Signals (was: I miss Drake)

[Don Galt]

>> if a car sitting at the next siding (car "A") heading the opposite
direction and had established its right to the single track before car "B",
then car "A" gets a green light and car "B" gets a totally blank signal -
no lights.  But this reverts to red over red shortly - don't know if the
approaching car has to go one block or just completely clear the switch
entering the siding.<<

Okay, but humor me even if all this is elementary:

Is this standard practice or a Pittsburgh idiosyncrasy?

What does the dark signal indicate different from red over red? If
operating rules forbid running a dark headblock anyway, then.....?

Note: I wrote the above after reading Jim's first message but before the
second. Maybe I now have a better idea, but the question still remains.

Was the blank signal simply informational?

I have no trouble with dark meaning "stop" - that is standard fail-safe
protocol - but am still wondering about its place in a hierarchy of
signals. If used as a cheap and easy way of indicating what to expect in a
unique situation without devising some new light combination, okay, but was
it an absolute prohibition or wasn't it? The way Jim expounds it in the
second message, I should think so. But then, how could anybody run it and
keep his job?

>> Do you think we have Uncle Don thoroughly confused by now, or should 
we work harder on it?! <<

Keep working, I can still see light.

D2