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Unusual Signals

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Unusual Signals 13/10/2014 at 11:52 #65026
Gwasanaethau
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509 posts
Hi all,

Here’s another question about strange signals in London. This time it’s about a signal I saw at City Thameslink. It was situated roughly half-way along the northbound platform. Unfortunately, when I saw it a couple of months ago, I was in a rush and didn’t have time to photograph it. I have since come across an identical one (see attachment) part-way down Platform B at St. Pancras. There were a couple more at St. Pancras’s Thameslink platforms pointing in various directions on both lines; and, it seems, yet more in and around Smithfield Sidings. Anybody know what they are? They seem to show normal 4-aspect signals – could they be miniature repeaters of some sort?

Thanks again!

Mark (Gwasanaethau)

EDIT: forgot to say: I apologise for the photo quality – it was taken with my phone.

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Last edited: 13/10/2014 at 11:53 by Gwasanaethau
Reason: Additional Info on Photo Quality

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Unusual Signals 13/10/2014 at 12:15 #65028
mfcooper
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707 posts
It is a mid-platform signal that is a combined 4-aspect signal and a Proceed On Sight Authority (POSA) signal.

The top right LED can display Green or Yellow, the bottom right LED can display Red or Yellow, giving a 4-aspect signalling sequence.

The top left and middle right LEDs display the flashing diagonal white lights that represent a proceed POSA aspect.

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Unusual Signals 13/10/2014 at 15:49 #65034
GW43125
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495 posts
" said:
It is a mid-platform signal that is a combined 4-aspect signal and a Proceed On Sight Authority (POSA) signal.

The top right LED can display Green or Yellow, the bottom right LED can display Red or Yellow, giving a 4-aspect signalling sequence.

The top left and middle right LEDs display the flashing diagonal white lights that represent a proceed POSA aspect.
I didn't realize it had a PoSA! I thought it was just a call-on!

You learn something new every day, as they say!

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Unusual Signals 13/10/2014 at 19:11 #65041
mfcooper
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" said:
...could they be miniature repeaters of some sort?
No repeating here. It is a stop signal. It just reduces the headway for the next train arriving into the platform.

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The following user said thank you: Gwasanaethau