Tony Duell wrote:
The same set of books describes the train descriptor
system used on the
London Underground. It consisted of a drum with 4 rows of pins on it.
Each pin could be in or out. The drum rotated past a 'write' device that
set the pins to one of 16 states corresponding to 16 different types of
trains. A 'read' device consisting of contacts/switches rotated inside
the drum, detecting the postitions of the pins in a given column. It was
an electromechanical version of the classic circular buffer with read and
write pointers... If anyone's in London and wants to see this device,
there's one in the London Transport Museum, BTW.
An excuse to visit England at last. (Wales, Scotland and Ireland have
been my only reason to consider crossing the Atlantic -- the "roots" gig
-- haven't done it yet anyway.) I know damned well there's nothing like
that over in the New York Subway Museum in Brooklyn.
--
Ward Griffiths
Dylan: How many years must some people exist,
before they're allowed to be free?
WDG3rd: If they "must" exist until they're "allowed",
they'll never be free.