London Banter - View Single Post - Train-numbers on the LU

Thomas Crame · February 21st 04, 09:31 PM posted to uk.transport.london

wrote in message ...
In article ,
(Peter Smyth) wrote:

"Thomas Crame" wrote in message
om...

The circle and H&C have a shared number series, I think.
The picc numbers were in the following series (in 1999):
250 - 257, 260 Cockfosters to Rayners Lane
261 - 267, 270 - 272 Cockfosters to Uxbridge
273 Spare at Acton Town (midday)
274 - 277 Northfields Midday Stablers
300 - 307, 310 - 317, 320 - 327, 330 - 337, 340 - 343 Cockfosters to
Heathrow
347 Acton Town Overnight stabler
351 - 357, 360 - 366 Arnos Grove to Northfields
371 - 373 Cockfosters Midday Stablers

Is there a reason why the don't use numbers ending in 8 or 9?

Peter Smyth

I think this started on the Northern Line, with the introduction of
programme machine working in the 1950s, and other lines followed suit. On
the programme machine rolls, the information for that train is stored in a
row of punched holes. Binary Coded Decimal is used a lot with the
programme machines and the various remote control of the IMRs etc. and
describers.

In BCD the decimal number is represented by the digits 0 and 1. The number
4 is represented by 100, 5-101, 6-110, 7-111, 8-1000, 16-10000 and so on.
This means an extra wire etc. for each extra digit. I suspect that this is
the reason. I have the info. on it somewhere, but not to hand.

The dutys (on the Northern Line anyway) also do not use 8 or 9. I can't
remember when it changed. It was a long while ago, but mot at the same
time as the programme machine introduction.

Roger

The programme machines use octal numbering, which is why they don't
use 8s or 9s. It's also impossible to have a train number beginning
with a number higher than 3 on a programme machine signalled line.

A few train numbers you won't see:
375 - This is used as the "Start of service" by a programme machine.
376 - Used for "End of service"
377 - Indicates the programme machine roll has come off the carrier,
as all contact fingers are made.