Circuit clips and detonator

Discussion in 'Infrastructure & Stations' started by 387star, 24 Nov 2011.

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  1. 387star

    387star Established Member

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    How do track circuit clips actually turn a signal to danger? Is it by short circuiting the absolute block? How does it fool the signal into thinking there are wheels on the line?

    Why are detonators placed. Is it where there are automatic signals and/or the signaller can't make contact? Why are additional detonators placed by signal boxes?

    Thanks
     
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  3. ralphchadkirk

    ralphchadkirk Established Member

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    Track circuits clips short the track circuit, which causes the the circuit to display occupied. Trains do the same, thus TC's are failsafe.
     
  4. Wyvern

    Wyvern Established Member

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  5. brillopad

    brillopad Member

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    How do clips work in an axle counted area ?
     
  6. ralphchadkirk

    ralphchadkirk Established Member

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    They don't. As far as I know.
     
  7. brillopad

    brillopad Member

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    Is there an alternative ?
     
  8. swt_passenger

    swt_passenger Veteran Member

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    GSM(R) cab to signaller comms, or IVRS if GSM(R) not yet live.
     
  9. ChiefPlanner

    ChiefPlanner Established Member

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    Track circuit clips and detonators - as final back up. AFTER communicating to the signaller by GSMR / CSR or whatever. Final protection after line blocked by communication.

    TC clips very effective (from one who has stamped them down in emergency a couple of times !)
     
  10. MrC

    MrC Member

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    Or, more likely, CSR/NRN. There's very little GSM(R) based (incl IVRS) stuff live yet. Also why, at least in the axle counter areas I know, there's extra lineside phones at regular intervals.
     
  11. swt_passenger

    swt_passenger Veteran Member

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    I'm just going by IVRS being used following Portsmouth Area resignalling with axle counters - so it isn't really a surprise that other methods are used elsewhere...
     
  12. driver9000

    driver9000 Established Member

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    Detonators provide an audible alert to drivers by exploding when crushed by the train wheels. Their use is much diminished now but at one time they were used at distant signals during times of poor visibilty. Today their use is to protect failed trains, possessions, hand signallers use them when holding a signal at danger and they are also used in emergency protection. Some signal boxes may still have operational detonator placers but I think these are few and far between.

    Track circuit clips don't work in axle counter areas as there are no track circuits for them to short out.
     
  13. MrC

    MrC Member

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    The vast majority of trains after the PARS implementation still use CSR. The GSM(R) base stations are live as they are over large chunks of the non-axle counter areas of the network but the trains haven't had the GSM(R) heads etc fitted yet. IVRS is a portable voice only GSM(R) handset available for use by non-CSR equipped trains (eg XC).

    AFAICT future axle counter resignalling such as Poole-Wool will retain CSR at least until full GSM(R) rollout over the train fleets has been completed.
     
  14. TEW

    TEW Established Member

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    Absolute Block being something entirely different, where there are no track circuits or axle counters. Only one train at a time is allowed between any two signal boxes with each train checked as it leaves a section to ensure it is complete and none of it remains in the section, the tail light being the indication that a train is complete. If an accident were to occur in an absolute block area which blocks the opposite running line then placing detonators may be the only method of protection, since a train on the opposite line may already have entered a long block.
     
  15. Old Timer

    Old Timer Established Member

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    Absolute Block sections do not normally have track circuits in the section.

    Track circuits may sometimes start at the distant signal, but in most situations are confined to the area from the Home signal berth to the Section signal.

    Where there is an Intermediate Block section, then the track circuits will extend from the berth track circuit at the Home signal to the IB Section signal.

    In the event of an incident affecting an adjoining running line, protection is by means of NRN, and then detonators.
     
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