The Waterloo and City line timetable (and maybe others - I think the
Central line is one) measures to the nearest 1/4 of a second. Things
like platform numbers and paths for empty stock are also all in there.

Did you mean 1/4 of a *minute* ? :-O

alex_t wrote:
The Waterloo and City line timetable (and maybe others - I think the
Central line is one) measures to the nearest 1/4 of a second. Things
like platform numbers and paths for empty stock are also all in there.

Did you mean 1/4 of a *minute* ? :-O


Of course not, I meant second.

Ahem...

Peter Corser wrote:

The half minute timing accuracy was down to the programme (sequence)
machines stepping every half minute. The timetables on the machines ran in
half-minute time (from 0300 to 0300 the next day) with 0 at midday - half
minute time was the most you could do within the limits of a computer
integer (8 bit - +/-32767 IIRC).

A good job they didn't have computers back in the 1920s then - the
Central London Railway used to run its off-peak trains at intervals of
one and seven-eighths of a minute. (Or 32 trains an hour.)
--
Joyce Whitchurch, Stalybridge, UK
=================================

Well, good luck to the Central line then - I'm pretty sure that trains
will miss 99,9% of all scheduled times by at least 1 second :-)

In message , Peter Corser
writes

The half minute timing accuracy was down to the programme (sequence)
machines stepping every half minute. The timetables on the machines ran in
half-minute time (from 0300 to 0300 the next day) with 0 at midday - half
minute time was the most you could do within the limits of a computer
integer (8 bit - +/-32767 IIRC).

The Central Line computer control ran internally to quarter minute timings,
but the Timetable software used in developing and printing of the published
timetables (and also the computer control timetables) could only cope with
half minute resolution.
Thank you I've saved that.
--
Clive.

"Paul Weaver" wrote in message
roups.com...
On 13 Mar, 22:29, "Peter Corser" wrote:
The half minute timing accuracy was down to the programme (sequence)
machines stepping every half minute. The timetables on the machines ran
in
half-minute time (from 0300 to 0300 the next day) with 0 at midday - half
minute time was the most you could do within the limits of a computer
integer (8 bit - +/-32767 IIRC).

8 bit would give you +-127, 16 bit is needed for 32767

The Central Line computer control ran internally to quarter minute
timings,
but the Timetable software used in developing and printing of the
published
timetables (and also the computer control timetables) could only cope
with
half minute resolution.

From noon until 3AM needs a signed integer capable of storing upto
1800 values for a half minute resolution, 3600 for quarter minute. 12
bits would do -2048 to +2047, capable of half minute, but not third or
quarter. 12 bits is 3, 4 bit words.

Nowadays of course 64bit time_t is the way to go, although I think
some libraries do 128 bit, which is a little extreme, although some
may say it doesn't go far enough. I think* a 256 bit time_t would be
capable of representing any measurable point in time, and then some.

*
seconds in creation (50 billion years): -- (86400*365.25*50000000000)
Measurable Units of time (plank time) in a second -- 1/(3.3 x 10^-44)
Measurable Units of time in creation (a*b)
~ 4.8 * 10^61
ln(4.8 * 10^61)/ln(2) == 205

Paul

Thanx for corrections - my memory was slightly befuddled & confused! It's a
long time since I did programme machine design for the original Heathrow
extension!

Programme machines (correctly known as sequence machines in most cases)
stepped in 30 second granularity. The whole system ran in two second time.
It is the two second time which requires the 16-bit width.

Bearing in mind that this system was designed in a railway signalling
pre-computer age using some relays and an individually designed set of
controls accomplished with electronic cards reducing the bit width was
always a necessity. The sequence machines ran on the plastic pianola roll
with mechanical fingers principle.

As an aside you may be aware that the train running numbers (set numbers)
shown in the time table were the direct digital equivalent of a hex number -
477 digital was stored as 477 hex and 477 was the highest number normally
used (there was also nothing between x78 and x99) which also saved bits (ot
sequence machine fingers).

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK



----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

On Wed, 14 Mar 2007 09:41:39 -0000, Peter Corser wrote:

As an aside you may be aware that the train running numbers (set numbers)
shown in the time table were the direct digital equivalent of a hex number -
477 digital was stored as 477 hex and 477 was the highest number normally
used (there was also nothing between x78 and x99) which also saved bits (ot
sequence machine fingers).

ITYM octal rather than hex...

On 13 Mar, 19:01, Paul Corfield wrote:
On 13 Mar 2007 11:18:41 -0700, "Paul Weaver"
wrote:

(snip)

With a 10-15 minute wait at the extremeties,
even at 9AM, it would be nice to see when trains are due. Some lines
have a live ETA, but the central line doesn't. The WAP service at
http://wap.tfl.gov.uk/tfldepboard/tends to break down whenever I try
and use it in anger

I think the argument is that services are typically so frequent that you
don't need a timetable. I don't agree with that myself and feel that at
places like Epping the minutes past the hour that trains are due to
leave should be provided on posters / leaflets.

(snip)


In the past I've picked up leaflets containing timetables for the
Metropolitan line, though I can't remember what stretches of the Met
they have covered - I suspect it was just the extremities, though they
also helpfully contained a line diagram that showed the pattern of
stopping, semi-fast and fast trains - something I can't find on the
TfL website.

Journeyplanner will display the exact timetable for Amersham, whilst
for Harrow-on-the-Hill it shows the exact times for an hour of morning
peak time and also late night trains, and Watford only has a selection
of exact times shown.

Mizter T wrote:

In the past I've picked up leaflets containing timetables for the
Metropolitan line, though I can't remember what stretches of the Met
they have covered - I suspect it was just the extremities, though they
also helpfully contained a line diagram that showed the pattern of
stopping, semi-fast and fast trains - something I can't find on the
TfL website.

I'm not sure about south of Baker Street, but I recall in the mid to late
1990s the Met used timetables on the boards not the "time between stations"
posters used for other lines. I think they also incorporated Chiltern.

In article , Peter Corser
writes
As an aside you may be aware that the train running numbers (set numbers)
shown in the time table were the direct digital equivalent of a hex number -
477 digital was stored as 477 hex and 477 was the highest number normally
used (there was also nothing between x78 and x99) which also saved bits (ot
sequence machine fingers).

Actually, I think you'll find that numbers on programme machine
controlled lines only went up to 377 - there were 8 bits for train
number.

The PM data I've seen wasn't organised by 8-bit byte, but simply had a
number of bits for each field. I thought that there were 6 minute bits,
5 hour bits, and a half-minute bit, but I could be misremembering here.

--
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: