[GreenKeys] Hughes Printing Telegraph for sale - EUR 9000 and up

[John Nagle]

On 5/15/2011 9:02 AM, greenkeys-request at mailman.qth.net wrote:
> Both the HUGHES and HOUSE machines reside in the Smithsonian.
> Probably in a locked storage room !

     The Science Museum in London has a Hughes Printing Telegraph.

     I've discovered that the one on sale isn't an 1875 Hughes unit,
despite what the auction materials say.  It's a German version made
by Gross and Graf, Berlin.

http://www.radiomuseum.org/r/grossgraf_telegraphen_apparattypen.html

It's from 1912 or later.  It's a beautiful piece of machinery, but
very late for that system, which was first used in 1855.  By the
time that thing was made, the first Morkrum start-stop machines
were already in use, finally solving the sync problem.  The
better Phelps system was already 30 years old at that point.

    The Hughes machines all had continuously rotating wheels
running in sync at each end.  These aren't step by step machines,
like stock tickers - that's a different approach. The Hughes
machines are much faster than tickers, but had sync problems.

    The original Hughes synchronization scheme was good
enough to keep both ends in sync once synchronized, because
each time a letter pulse was sent, the mechanism drove a
pawl into a gear, correcting slight character-time sync errors.  But
operators had to start up communications from a cold start by sending
a "dash" with the receiver stopped, then sending "AAAAA" to make
sure they were in sync, in case the governor had to be tweaked.
If a Hughes machine got out of sync, it would not resynchronize until
the operator shut down the line and forced the sender to shut down and
do the resync thing.

     The Phelps system from the 1880s had a timeout mechanism, so
that if no characters were sent for about four character times,
it would go to its idle state with the typewheel stopped at the
dash character.  This made it self-synchronizing.  It wasn't
full start-stop, like a Teletype, but they were getting close.
It could thus be used on multidrop and broadcast systems,
or run unattended, unlike the Hughes system.  Phelps machines
were in use as late as 1950.  Has anyone ever seen one?

     (I was at one time looking into building a replica Phelps
machine, and got far enough to start engraving a typewheel,
but didn't go on with the project.)

				John Nagle