Block signaling vs slot signaling

[Thomas and Duck Fan]

Lately, I've just heard about this thing called Slot Signaling, something said to be different from block signaling. Is there anybody here that can tell me the difference between block and slot signaling?

[jim.snowdon]

It might help if we knew where you heard about this 'slot signalling'.

[micknich2003]

I have had a life time interest in signalling, and I spent the last thirty five years of my working life as a signalman, but never heard of your question. Are you confussed with Slotted Signals or Slotted Post signals?

[rogerzilla]

It's not another term for moving block, is it?  Moving block should allow more capacity but needs in-cab signalling.

[Flying Pig]

This is the only reference I could find online:

 

https://www.simsig.co.uk/Wiki/Show?page=usertrack:glossary:slot

 

 

[dunnyrail]

Sounds very much to me like someone who knows a little bit about the use of Slotting in a signal box trying to explain it and getting mixed up with permission, authority to proceed and block signalling procedures. 

[Michael Hodgson]

 

 

The object of block signalling is to prevent more than one train being in a block section on the same line at the same time.   It became a statutory requirement for passenger railways under the Regulation of Railways Act 1889, along with the provision of conintuous brakes on all vehicles in a passenger train and interlocking between signals and points.

 

Slotting is a method in semaphore signalling whereby two signal boxes exercise control of a signal arm, that is both boxes have to pull their relevant lever in order to clear the signal.

[Edwin_m]

50 minutes ago, Michael Hodgson said:

Slotting is a method in semaphore signalling whereby two signal boxes exercise control of a signal arm, that is both boxes have to pull their relevant lever in order to clear the signal.

And these days is used more widely for a situation where two signal boxes have to operate controls to clear the same signal, including for colour-lights and relay or computer interlockings where there is no physical slotting mechanism involved.  

[Banger Blue]

2 hours ago, Flying Pig said:

This is the only reference I could find online:

 

https://www.simsig.co.uk/Wiki/Show?page=usertrack:glossary:slot

 

 

 

"Requesting a Slot" immediately sprang to mind when I read the OP.

 

This is how Reading TCD receives a slot request from the Reading Station Signaller, as you can see from the pic below, there is a separate slot dependent on platform being used.

 

An audible alert is received and the green circle will flash. The route gets set, by the depot controller, from the entry arrow [ENTE] to the chosen siding then once the slot is accepted by clicking on the circle, this will then turn solid green, this then allows the Signaller to set their route & clear the respective signal.

 

[The Stationmaster]

41 minutes ago, Banger Blue said:

 

"Requesting a Slot" immediately sprang to mind when I read the OP.

 

This is how Reading TCD receives a slot request from the Reading Station Signaller, as you can see from the pic below, there is a separate slot dependent on platform being used.

 

An audible alert is received and the green circle will flash. The route gets set, by the depot controller, from the entry arrow [ENTE] to the chosen siding then once the slot is accepted by clicking on the circle, this will then turn solid green, this then allows the Signaller to set their route & clear the respective signal.

 

That reminds me of something that was siad by a Shunter at Didcot when Reading panel first took control of the Didcot area - 'Up until now when I winted the road I'd shout across to the 'box, now I've got to 'phone Reading panel to get the road'.

This system at TVSCC clearly avoids the need to try to shout between Reading and Didcot or make a 'phone call - so it is genuine progress.

 

PS. Just had a thought I wonder if somebody has got confused over single lines worked by acceptance levers or switches or by interlocking levers?

 

Edited April 30, 2023 by The Stationmaster

[Thomas and Duck Fan]

It was actually mentioned in this video: https://youtu.be/OqwiAkf89qo

[Wheatley]

1 hour ago, Thomas and Duck Fan said:

It was actually mentioned in this video: https://youtu.be/OqwiAkf89qo

Any clue as to where so we don't have to sit through all 12 minutes of it ?

 

[Thomas and Duck Fan]

Look in the chapters section

[Jeremy Cumberland]

"Happy April fools day" might suggest the video is not entirely factually accurate.

 

The description in the video has a lot of similarities with the Abbot's Ripton accident in 1876, but the narration mixes up some things and makes contradictory statements, but it is an April Fool's joke, so that's only to be expected.

 

Slotted post signals were an important contributory factor at Abbot's Ripton (the signal arm - normally kept at clear, as the video says - froze in the post), but the video makes no mention of slotted post signals and gives weight of snow forcing the arm down as the reason for this particular signal being clear (which, incidentally, would make keeping signals normally clear irrelevant). I seem to recall weight of snow giving a false aspect to be the primary cause of a different accident, but I can't remember which (Castlecary, perhaps).

 

The video makes a number of other valid points about the development of railway signalling, but some of these are irrelevent (AWS would not have made an iota of difference to the accident as described, for example), and others aren't really presented in a logical manner.

 

Abbot's Ripton used absolute block signalling, although in a simpler form to that found in the twentieth century.

 

2 minutes ago, Thomas and Duck Fan said:

Look in the chapters section

It doesn't mention "slot signalling", and I didn't hear the word "slot" used in the entire video.

[Thomas and Duck Fan]

There’s clearly a chapter labeled safety systems! That’s a clear-enough giveaway!

[Bucoops]

5 hours ago, Thomas and Duck Fan said:

There’s clearly a chapter labeled safety systems! That’s a clear-enough giveaway!

 

Please can I suggest you re-visit your posting method as you are coming across rather grumpy when people are trying to help 🙂

[Wheatley]

9 hours ago, Thomas and Duck Fan said:

There’s clearly a chapter labelled safety systems! That’s a clear-enough giveaway!

CBA. 

 

Never heard of 'slot signalling', only the slotting described above by others. Ex-signalman and Signalling Inspector. 

Edited May 2, 2023 by Wheatley

[ejstubbs]

10 hours ago, Thomas and Duck Fan said:

There’s clearly a chapter labeled safety systems! That’s a clear-enough giveaway!

 

Having watched it through several times I've not found any mention of "slot signalling", or even the word "slot" in that section, or anywhere else in the video.  I did wonder if it might have appeared on screen as a result of a glitch in the automatically generated subtitles, which are notoriously unreliable (a particularly egregious example from that video is the word "semaphore" appearing in the subtitles as  "some of four"!)  However, again, I found no occurrence of the words under discussion in said subtitles.  The only other possibility I can think of is that the OP misheard "block" as "slot" - but the only person who could verify that is the OP, who seems to be taking a somewhat belligerent attitude to any attempts to throw more light the supposed origin of the information in their posts.

 

My conclusion: nothing to see here, move along.

[The Stationmaster]

13 hours ago, Thomas and Duck Fan said:

It was actually mentioned in this video: https://youtu.be/OqwiAkf89qo

Thanks, that was really good for laughs at some of the amazing rubbish the voiceover came out with.   Don't know about an April Fool but a lot of it struck me as sheer ignorance.  As for showing Western semaphores and saying they could be held off by snow it was utter nonsense.  I've worked in conditions where we had snow several feet deep and not a single one of our signals dropped to off because of the weight of snow on the wire run - our biggest problem was signals frozen 'on' .  But alas one point which seems to have been assumed by it but wasn't clearly made was that at Abbots Ripton, as was not uncommon practice in those days, signals normally stood at 'off' and were only returned to danger immediately after a train had passed - hence they could readily freeze at 'off'

 

The video was basically a concoction of abysmally researched and barely understood past railway incidents woven into some irrelevant pictures, some cuts from TTTE film, and a load of nonsense resulting from lack of understanding of the subject.  Good fr the occasional laugh but rather worrying that such an amateurish effort should be presented as a sort of history of some aspects of signalling.

 

And I couldn't get any chapter numbers to come up but I suspect that if it had emerged anywhere the 'slot' business might have referred to slotted signal posts although they do not seem to be specifically mentioned in Henry Tyler's Report regarding the Abbots Ripton collisions although he did comment on the design of signals and criticised the fact that they were normally left 'off'

[5BarVT]

A fun video.

Did anyone else notice the GWR ATC ramp in one of the shots in the AWS chapter?

A nice bit of fun, but not something to reference in a technical definition!

Paul.

[roythebus1]

The only thing I could think of apart from slotted signals is confusion between absolute block and permissive block.

 

There's some cupid stunts around making videos at times!

[Bucoops]

31 minutes ago, roythebus1 said:

The only thing I could think of apart from slotted signals is confusion between absolute block and permissive block.

 

There's some cupid stunts around making videos at times!

 

That's a different kind of slot?

[roythebus1]

Quite. :)

[Flying Pig]

On 30/04/2023 at 11:29, The Stationmaster said:

This system at TVSCC clearly avoids the need to try to shout between Reading and Didcot or make a 'phone call - so it is genuine progress.

 

 

Returning to Simsig, the Swindon edition I played back in about 2004 used a slot to control the Thingley to Bradford Junction single line section.

[The Stationmaster]

On 08/05/2023 at 12:20, Flying Pig said:

 

Returning to Simsig, the Swindon edition I played back in about 2004 used a slot to control the Thingley to Bradford Junction single line section.

Interesting.  I don't know what happened as a result of Westbiury resignalling but I presume the line became Single Line TCB  using  Acceptance Switches.  Prior to that it was worked by NSKT controlled by the Bradford Jcn Signalman.