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Rosarie AOCR

Discussion concerning level crossings

Re: Rosarie AOCR

Unread postby Pete2320 » Thu Jul 27, 2017 12:50 pm

AndyB wrote:It also has to be remembered that AOCR is AHB without barriers! Presumably the console in the supervising cabin only proves the wigwags are operating, where AHBs prove barriers down or failed.

The barriers at an AHB are not proved down in anything. The working or failed indication onlyindicates that the crossing has not been operating for more than a certain time (I forget how long). Operating includes any activation of the relay equipment that is not followed through by the full sequence and such as the barriers being not fully raised.
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Re: Rosarie AOCR

Unread postby StevieG » Thu Jul 27, 2017 9:12 pm

Pete2320 wrote:The barriers at an AHB are not proved down in anything. The working or failed indication onlyindicates that the crossing has not been operating for more than a certain time (I forget how long). Operating includes any activation of the relay equipment that is not followed through by the full sequence and such as the barriers being not fully raised.
Drifting a little further from AOCRs (only temporarily I hope), may I add to your info., Pete, some 1980s 'operating' dept. memories of my own, from the one AHB (on double track; replete with flashing red neon 'Another Train Coming' signs) that we supervised from a large BR(ER) power box.

As I recall it, including from sight of its control tables at the time, key wording read something like :
"Crossing maintained Normal [i.e. powered-up, ready, but not activated and barriers up; so, was when the "Raised" indication was lit] by..." - followed by detail/listing of all the relevant track circuits to be clear (including some conditional on the intervening 'R'-button-equipped 3-aspect Automatic C/L signals being free of approach locking if at Danger); and the several treadles (at least 10) to be detected as in their Normal (not operated) position.
Whenever any of these conditions was no longer true, normally of course caused by a train 'Striking in' and being on the approach side of the crossing, then the crossing sequence should have been activated and maintained, and the "Working" indication replaced the "Raised".

It seemed that the "Working" defaulted to "Failed" if, either (of course) power was lost, or if the crossing's "Raised" status was not restored within a specific time period, presumably judged as being long enough for the crossing to have become normalised after passage of one train on both lines.
But in fact it was not so unusual to see it change to "Failed", usually if kept activated for longer than the designated time by -
- a train on one line passing the '2nd train strike-in' (2ndTSI) before a nearer train on the other line had gone clear, then also followed by a third train on the first's line passing that 2ndTSI before the second train had gone clear; or
- a slow-moving Up direction train departing from the station or yard two signal sections away.

So, apart from the absence of barriers, would an AOCR's operation, and indications in the box, have been much the same, or identical ?
BZOH

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Re: Rosarie AOCR

Unread postby Mike Hodgson » Thu Jul 27, 2017 11:45 pm

StevieG wrote:
Pete2320 wrote:The barriers at an AHB are not proved down in anything. The working or failed indication onlyindicates that the crossing has not been operating for more than a certain time (I forget how long). Operating includes any activation of the relay equipment that is not followed through by the full sequence and such as the barriers being not fully raised.
Drifting a little further from AOCRs (only temporarily I hope), may I add to your info., Pete, some 1980s 'operating' dept. memories of my own, from the one AHB (on double track; replete with flashing red neon 'Another Train Coming' signs) that we supervised from a large BR(ER) power box.

As I recall it, including from sight of its control tables at the time, key wording read something like :
"Crossing maintained Normal [i.e. powered-up, ready, but not activated and barriers up; so, was when the "Raised" indication was lit] by..." - followed by detail/listing of all the relevant track circuits to be clear (including some conditional on the intervening 'R'-button-equipped 3-aspect Automatic C/L signals being free of approach locking if at Danger); and the several treadles (at least 10) to be detected as in their Normal (not operated) position.
Whenever any of these conditions was no longer true, normally of course caused by a train 'Striking in' and being on the approach side of the crossing, then the crossing sequence should have been activated and maintained, and the "Working" indication replaced the "Raised".

It seemed that the "Working" defaulted to "Failed" if, either (of course) power was lost, or if the crossing's "Raised" status was not restored within a specific time period, presumably judged as being long enough for the crossing to have become normalised after passage of one train on both lines.
But in fact it was not so unusual to see it change to "Failed", usually if kept activated for longer than the designated time by -
- a train on one line passing the '2nd train strike-in' (2ndTSI) before a nearer train on the other line had gone clear, then also followed by a third train on the first's line passing that 2ndTSI before the second train had gone clear; or
- a slow-moving Up direction train departing from the station or yard two signal sections away.

So, apart from the absence of barriers, would an AOCR's operation, and indications in the box, have been much the same, or identical ?


Although barriers are not proved down in an AHB, if they are obstructed or do not lower properly that is one of the conditions that will cause the crossing to fail. There isn't/wasn't a uniform way of providing AHB indications in the box. Whilst many of them are indicated by status lamps on control panels or on small standardised crossing control boxes with switches for standby power, switching to local control and acknowledging crossing failure, quite a lot are/were indicated by a 3-position needle indicator similar to those commonly used on block shelves for signal or point indications etc.

The needle type of indicator is fed from a single line wire from the crossing, with one polarity being used to indicate "Barriers Raised" (= both of them within a few degrees of vertical), the polarity being reversed when the crossing is actuated causing the needle to swing over to the opposite position labelled "Working" or similar. Despite this change in indication however the barriers would still be fully raised for about the first 10 seconds after strike-in as the wig-wags go through amber and a few seconds on red before lowering commences. Loss of the line wire or assorted other faults result in no voltage being applied to the line, the needle dropping to mid-position, this being interpreted as Crossing Failed. Whilst the control prinicples for an AOCR might be the same as an AHB, the indication could not quite be identical, as at least the wording "Barriers Raised" would be inappropriate.
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