On 17/05/2012 18:59, Steve Fitzgerald wrote:
In message , "
writes

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?

The area has been totally re-signalled with the work to remove the
centre tracks. There are no longer any booked reversers at Whitechapel
so there is no need to keep the signal cabin manned. When it is switched
out and the As are illuminated, trains can be authorised past failing
signals by the rulebook under failure conditions without the need for
someone to go on the track and secure the points and then be authorised
by the signaller. If the points are not secured the As won't illuminate.

What gave an indication earlier that the Whitechapel signals were
semi-automatic, if they didn't have the illuminated As?