"Andy" wrote in message
...

But don't the Electrostars have the cameras on the train, so there is
no transmission system needed, other than feeds into the train's own
systems.

You can see the cameras down the side of the train in this image:

http://www.railfaneurope.net/pix/gb/...377-432-mt.jpg

The Northern and Central lines are more complex of course, there
probably isn't space for cameras on the side of the cars.


But technology can allow for smaller cameras and easier installation, can't
it?

Retractable mirrors can also be an option in some places, though granted
they might not be effective everywhere on LUL.

"D7666" wrote in message
...
On Nov 30, 4:47 am, Charles Ellson wrote:

relays drop out causing an alarm;

reset up to three times in
succession before someone is sent

Nope. Respond at first alarm with an emergency fault. At least thats
how we do it on ''my'' bit of underground infrastructure.

--
Perhaps there is a risk that something happened, and people might be on or
around the tracks? You don't want to accidentally fry them.

On Wed, 3 Dec 2008 00:19:41 -0000, wrote:

"D7666" wrote in message
...
On Nov 30, 4:47 am, Charles Ellson wrote:

relays drop out causing an alarm;

reset up to three times in
succession before someone is sent

Nope. Respond at first alarm with an emergency fault. At least thats
how we do it on ''my'' bit of underground infrastructure.

--
Perhaps there is a risk that something happened, and people might be on or
around the tracks? You don't want to accidentally fry them.

Going back to the ancient version that I experienced, the "reset up to
X times before sending someone out" was to allow for transient faults
caused by wind-blown metallic debris, flowing/pouring water etc.

There should not be anyone on the tracks unless train crew have let
them out after taking appropriate measures which would include
application of a SCD; this should result in immediate re-tripping when
it is attempted to reset the supply breaker rather than the delayed
tripping which might be caused by debris or dangling bits of train.
AFAIR (this was before radio was in use) evacuation was allowed to
take place as immediately as necessary in the absence of
communications after X seconds had passed since the application of the
SCD to give time for the "reset X times then leave the power off and
investigate" procedure to be achieved; otherwise if communication was
available and/or there was no immediate need to evacuate then things
proceeded as required/appropriate.

On Dec 3, 12:17*am, wrote:
"Andy" wrote in message

...

But don't the Electrostars have the cameras on the train, so there is
no transmission system needed, other than feeds into the train's own
systems.

You can see the cameras down the side of the train in this image:

http://www.railfaneurope.net/pix/gb/...377-432-mt.jpg

The Northern and Central lines are more complex of course, there
probably isn't space for cameras on the side of the cars.

But technology can allow for smaller cameras and easier installation, can't
it?


Sure, but they still have to pertrude from the side of the train in
order to cover the doors etc. My understanding is that the current
Northern and Central line tube stock is a very tight fit to the
loading gauge in a few places and even a couple of millimeters would
be too much extra for trains to run safely at line speed.

Retractable mirrors can also be an option in some places, though granted
they might not be effective everywhere on LUL.

Andy wrote in news:2f81c2b5-8894-48a0-a547-
:

On Dec 2, 6:55*am, "Clive D. W. Feather" cl...@on-the-
train.demon.co.uk wrote:

The Northern and Central Lines have this, but that's mostly because
there's no room to retro-fit the monitors in tube stations.

I was involved in specifying the video transmission system for the Central
Line, and the rationale given at the time was that they wanted (or maybe
were required) to allow the driver to see the images after moving off.

Peter

--
Peter Campbell Smith ~ London ~ pjcs00 (a) gmail.com

"Peter Campbell Smith" wrote

I was involved in specifying the video transmission system for the Central
Line, and the rationale given at the time was that they wanted (or maybe
were required) to allow the driver to see the images after moving off.

This RAIB report explains why.
http://www.raib.gov.uk/cms_resources...g_Broadway.pdf
In this case, the train operator was apparently too concerned about checking
signal aspects (he'd been involved in a previous SPAD) that he didn't notice
in the monitor that the passenger was being dragged along the platform.

Peter

On Dec 2, 9:55 pm, Charles Ellson wrote:
On Tue, 2 Dec 2008 13:17:18 -0800 (PST), D7666
wrote:

On Nov 30, 4:47 am, Charles Ellson wrote:

relays drop out causing an alarm;

reset up to three times in
succession before someone is sent

Nope.

Well, it's been a few years since someone demonstrated the process to
me.

Respond at first alarm with an emergency fault. At least thats
how we do it on ''my'' bit of underground infrastructure.

The same procedure for both unreproducable trips and persistent trips?

Maybe we are at cross purposes here.

I thought you were talking about earth faults - as in ''fully neggy
earth'' or ''full pozzy earth'' as they like to say - not traction
trips.

Earth faults of the nature I was referring to usually don't cause
traction trips or if they do they are usually single events. These
earth faults are indicated the line *service* control room. They are
responded to at first event as experience suggests they are generally
caused by debris that needs shifting, sometimes by a very recently
deceased mammal, or sometimes by a cracked pot (no not an anorak on
the line) in which case the quick fix is smash the pot right out of it
and sort it out in engineering hours.

Traction trips yes, I agree, they re-close the breakers a couple of
times - maybe it is the three you wrote - before investigating - thats
done by the *power* control room. Moving faults i.e. caused by a train
defect make interesting work - power control room has no indication of
trains.

--
Nick

"Peter Campbell Smith" wrote in message
...
Andy wrote in news:2f81c2b5-8894-48a0-a547-
:

On Dec 2, 6:55 am, "Clive D. W. Feather" cl...@on-the-
train.demon.co.uk wrote:

The Northern and Central Lines have this, but that's mostly because
there's no room to retro-fit the monitors in tube stations.

I was involved in specifying the video transmission system for the Central
Line, and the rationale given at the time was that they wanted (or maybe
were required) to allow the driver to see the images after moving off.


Hamburg also has an on-board system for platform monitoring.

In article , Charles Ellson
writes
In other words, the resistors keep the rails at the +420V/-210V position
*unless* something else happens to alter this. Hence "loosely tied". But
at all times (absent a major short) the two rails are 630V apart.

They can be both at the same potential if there is a break between one
conductor rail feed and the substation (or only one of the pair of
switches feeding from the next section is closed) and you have a train
in section.

Or if the feed is broken upstream of the resistors.

Good point that I'd overlooked. Thanks.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Please reply to the Reply-To address, which is:

On Wed, 3 Dec 2008 02:30:28 -0800 (PST), wrote:

On Dec 2, 9:55 pm, Charles Ellson wrote:
On Tue, 2 Dec 2008 13:17:18 -0800 (PST), D7666
wrote:

On Nov 30, 4:47 am, Charles Ellson wrote:

relays drop out causing an alarm;

reset up to three times in
succession before someone is sent

Nope.

Well, it's been a few years since someone demonstrated the process to
me.

Respond at first alarm with an emergency fault. At least thats
how we do it on ''my'' bit of underground infrastructure.

The same procedure for both unreproducable trips and persistent trips?

Maybe we are at cross purposes here.

I thought you were talking about earth faults - as in ''fully neggy
earth'' or ''full pozzy earth'' as they like to say - not traction
trips.

Earth faults of the nature I was referring to usually don't cause
traction trips or if they do they are usually single events. These
earth faults are indicated the line *service* control room. They are
responded to at first event as experience suggests they are generally
caused by debris that needs shifting, sometimes by a very recently
deceased mammal, or sometimes by a cracked pot (no not an anorak on
the line) in which case the quick fix is smash the pot right out of it
and sort it out in engineering hours.

Traction trips yes, I agree, they re-close the breakers a couple of
times - maybe it is the three you wrote - before investigating - thats
done by the *power* control room. Moving faults i.e. caused by a train
defect make interesting work - power control room has no indication of
trains.

Aaargh! Some more brain cells have now woken up - I've just realised
that the device I _saw_ demonstrated some years ago was the breaker
operated by shorting the tunnel wires (solenoid drops heavy metal ball
on end of string which yanks out switch - it was a few years ago).
Regarding the above, I was possibly thinking simultaneously of earth
faults and the effect of SCDs; in the case of LU's (nominally)
non-earthed supply it demonstrates some of the reasons why such types
of supply are generally frowned upon and need special protection
measures.