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In a run of automatic signals, why do we have a couple of non-automatics?

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In a run of automatic signals, why do we have a couple of non-automatics? Yesterday at 07:13 #130291
pedroathome
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Giantray in post 130290 said:
pedroathome in post 130218 said:


Going to add here, not forgetting the difference in E and R replacements. R being guaranteed, E not being guaranteed (Or is it other way around).

Going slightly off topic, when would R replacements have started to become common?
'E' Emergency replacements were not lamp proved. The indication in the signal box for these was just to show the button had been operated, there was no proof the signal was actually at danger. 'R' replacements have become more common as the move from old lamp proven signals changes to LED aspect signal heads. These are relied upon to be at danger when replaced and can be used to protect Line Blockages and Engineer's Possessions unlike 'E' replacement auto signals that must not be used.
I'm sure that Mr Fulcher or someone else will be around to correct me here if I'm wrong, but its not down to the type of signal head, but rather the circuitry for it.

E replacements, as you say, were not lamp repeated back to the box, and I believe that all relay circuits needed for these did not need to be fail safe relays.

R replacements however, I assume were aspect fed back to the box, and used relays that would correctly indicate the danger aspect back to the signaller. I believe, but again, could be wrong, that in modern solid state installations, every aspect is repeated back to the box in question.

As a point of reference here, Remember, if a relay does not drop, it dosen't matter what kind of signal head the signal is, the relay is still telling the signal to display one aspect, when it should be the other.

James

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In a run of automatic signals, why do we have a couple of non-automatics? Yesterday at 21:26 #130310
manadude2
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Thank you everyone for the insights, it's been a very interesting read and I've learned a lot of new things!
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In a run of automatic signals, why do we have a couple of non-automatics? Today at 03:46 #130318
GeoffM
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pedroathome in post 130291 said:
I believe, but again, could be wrong, that in modern solid state installations, every aspect is repeated back to the box in question.
Well, in this case the interlocking is usually in the signal box and calculates all the aspects, and sends the instructions out over the data link. So all it proves is that it tried to liven up bit 7 of telegram 15 and the trackside module indicated that return current was detected, so we hope the red lamp (or components making the light red) was the one plugged in to the right socket...

SimSig Boss
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