On 17/05/2012 08:06, Steve Fitzgerald wrote:
In message , "
writes

I also notice that they have converted the signals in that area from
automatic to semi-automatic, or floodgate signals, as they are called
on the Northern Line. Why is that?

Not floodgate signals at all. Semi-automatic (controlled) signals which
are to be treated as automatic in certain circumstances. When the points
are proved secured, the signal cabin can be put into King (the King
lever is thrown) and worked as through running.

Just going on what they call them on the Northern Line, though yes,
they are semi-automatic. The illuminated A under the signal itself
indicates that they are in automatic mode.

Illuminated As are generally used on floodgate signals on the Northern,
Picc and District that I know of but not exclusively.

I've seen the illuminated As at Waterloo northbound on the Northern and
at Russell Square on westbound track.

If the signals were earlier semi-automatic at Whitechapel, then why did
they just install illuminated As now?