"Peter Corser" wrote in message
...

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.

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK

Think of the problems 'extended hours' is causing on programe machine sites.
(ok it not huge but running a train pass 3am is not that simple)
Andy