PC Aws Cab Change End Lever

Discussion in 'TSW General Discussion' started by Rudolf, Mar 11, 2020.

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  1. Rudolf

    Rudolf Well-Known Member

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    Hi,

    Can any one explain what the AWS Cab Change End Lever does in relation tot he AWS Isolation switch? E.g. the class 47 has this setup.

    I am curious how to use it, especially if you change cab.
     
  2. stujoy

    stujoy Well-Known Member

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    If you wish to use AWS you need the Cab Changeover ON in the cab you are driving from and OFF in the cab at the other end. The same applies to the AWS isolator, ON in the cab you are in, OFF at the other end. By default these are in the OFF position so there is no need to check the other end of the cab if you are just starting out at one end.

    When changing from one cab to the other, you need to ensure you turn them both off in the cab you are leaving and then on in the cab you change to. If you don’t, when the AWS sounds you won’t be able to cancel it.
     
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  3. DominusEdwardius

    DominusEdwardius Well-Known Member

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    Effectively in BR days AWS was always unisolated unless there was a problem (the isolation lever was sealed with a bit of lead). That means effectively the two AWS units is always active when the system has power. This presents a bit of a problem in that you'd get AWS warnings in both cabs (or worse at both ends of a DMU!) which of course would be impossible to cancel given you're not there to press the reset button. The system doesn't know exactly what cab is in use at any one time (its literally a couple of electromagnetic valves and timing reservoirs and isn't exactly smart on these older locos). You also can't just isolate the AWS as that would mean you could potentially just drive around with no AWS which entirely defeats the point!

    Effectively the AWS change end lever when switched to off locally isolates the AWS in that cab rendering it effectively inert, but not isolated. There is usually also a built in feature on locos where if you try and activate both AWS units on a loco you will be unable to cancel the AWS horn when you switch the second unit on. Similarly if you don't activate either unit you won't be able to release the train brake.

    The Procedure is quite simple when changing cabs, just switch the change end lever in the cab you're leaving to off, and switching the unit in the 2nd cab to on when you enter (assuming the AWS units aren't isolated entirely).
     
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  4. Trim

    Trim Active Member

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    Just in case DominusEdwardius reply isn't clear enough:

    In the cab you are NOT driving from:
    • The AWS Cab Changeover Lever must be set to Off
    • It does not matter what position the AWS Isolation Switch is in
    In the cab you are driving from:
    • The AWS Isolation Switch must be set to Unisolated
    • The AWS Cab Changeover Lever must be set to On
    Since these are set to Off/Isolated by default, what this means is that:
    • When you join a train, you don't need to do anything in the rear cab, so far as AWS is concerned, and in the front cab you set both levers.
    • When you change ends, you turn the AWS Cab Changeover Lever to Off before leaving the cab, and in the other cab you need to set both levers (the AWS Isolation Switch may already be set).
    The Class 101 is an exception in that it does not have an AWS Cab Changeover Lever. You need to set the AWS Isolation Lever to Unisolated in the cab you are driving from, and the position of the lever in the rear cab does not matter. When you change ends, you don't need to do anything in the cab you are leaving.

    Both levers/switches may have slightly different names, depending on what it is you are driving.

    If you want to turn off AWS (having previously had it turned on), then you need to make sure that the AWS Isolation Switch is set to Isolated in both cabs. It does not matter whether or not you leave the AWS Changeover Levers in On or Off, but in real life of course you would turn these off as well. In the Class 101, it does not matter what the rear cab AWS Isolation Lever is set to; only the one in the front cab matters.
     
    Last edited: Mar 11, 2020
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  5. Rudolf

    Rudolf Well-Known Member

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    Thanks for your quick answers
    Trim and
    stujoy and
    DominusEdwardius
    This is very helpful. Google failed me here! I will use this info in the Route Guides I am creating, of course giving you credits there.
     

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