Strange Marker at Ickenham

It may appear strange to you, but every single platform headwall on LU has one!!

It indicates that the train radio in the section ahead is defective.

I still say it looks strange - with the white X looking like someone's been down to cancel out the sign (as it's no longer used and they can't be bothered removing it), rather than it being an official looking sign :-)

Yes, it was Westbound

Not correct I'm afraid.

If a single connect cell was down, then it is treated as a localised failure of the train radio system. The above pictured board may be utilised.

Under those circumstances, the rules state that only 1 train on each line may enter the affected area at one time - so the cell is treated as one signal block section in effect.

If any more than 1 cell fails, then you move into the realms of having hand signalpersons on platforms, and trains running empty through the affected area etc.

If the entire radio system fails, then the logistics of having every platform manned, every train double-manned, and every train running empty moves into the realms of suspending the service.

In this particular case, the sign at Ickenham was displaying incorrectly, as there was not a failure of the radio system in that area last week.

Presumably all the 'signal bleed' of the old Storno radio system that occurred with a limited number of channels having to be utilised imaginitively to cover the entire railway has been completely eliminated by cell technology.
I assume that all trains and mobiles on all lines can now be called individually giving privacy to any required conversation and thus removing the possibility of 'overhearing' and potential misdirection as a result thereof.

So the question is just how large is a cell? Obviously they can be engineered to be of different sizes of coverage but presumably that has been planned to operating requirements. Is a cell therefore the area between two underground stations or more than two underground stations, for instance a traction current section, or simply a geographical area? I would also assume that the limitations of the original individual line train radio systems have been overcome with integration of certain channels network wide allowing universal access for police and emergency services as well as some standard operating procedures.

Each station has its own cell and in theory each cell extends halfway to adjacent stations where that station's cell takes over.

Yes. One of the two. I don't actually know but would presume it to be the latter except where trains on different lines actually share the same tracks.

Line meaning track or service.

Take the area mentioned in this thread. Now imagine a series of "bubbles" along the line from Uxbridge. The first surrounds Uxbridge station and extends as far as roughly half-way to Hillingdon. There the next bubble starts, and stretches over Hillingdon and half-way to Ickenham. And so on.

So each platform is technically half-way through each cell.

In multi-line areas, for instance Finchley Road to Wembley Park, the cells are the same, but the set-up of respective train equipment means that each train will talk to the correct controller for the line on which they are operating. This means that "usually" a Jubilee Line train hitting the controller button, will be connected to the Jubilee Line controller.



If a train operator was at that platform, and technically half-way through the cell, they would probably already be aware that the radio had failed - the display on the in-cab radio would tell them of the loss of radio, and I believe there is an audible beeping to attract them to this.

As for correcting the sign, our train operators are there to driver their trains, and our station staff are there to look after station-based items. So unless there was nobody available, we would look to the station supervisor to correct the sign.

So a t/op arriving at Ickenham and seeing this board when the radio is working, would presumably just double check the radio display to confirm that it is working? Would they specifically contact anyone about the sign, or would it just be something passed on next time they're in contact with the line controller?