[GreenKeys] Right Priced M28 on eBay

[Teletypeparts]

Ralph,

I only have to add that 66 WPM was the European standard for Telex, hence the 66 WPM 32 ASR Western Union Telex we see a lot of.  

Wayne
KB1FDW
Former Crypto USAF Tech.




-----Original Message-----
From: Ralph Irish <w8roi at wowway.com>
To: greenkeys <greenkeys at mailman.qth.net>
Sent: Tue, Dec 31, 2013 1:03 pm
Subject: Re: [GreenKeys] Right Priced M28 on eBay



This looks like an above average machine for its vintage.  I offer one caveat, however.


The tag shows, on one line, "FOR LIST OF UNITS SEE INSTR. BOOK KAM 44/TSEC"


When I was in the Navy, "TSEC" represented Top Secret equipment, usually crypto related.


There were special machines made by Teletype for the Navy which had non-standard speeds.
This was a security measure.  I think that many of our Crypto 28s operated at 65 WPM,
with a lot of different parts involved, other than a gear set.  The idea was that it
would be difficult to sneak a line in series with the selector magnets for illegal 
copies of messages in another location.  And, at some point, the  TEMPEST  rules went
into effect, due to situations where a simple coil of wire not far from a decoding device
could pick up useful information.


66 WPM is/was a so called 'standard speed' at one time, but just one WPM less often meant
garble and a high error rate.  I have a three speed gearshift on my 28ASR that has 60/66/100
WPM.  I'd much rather it had 60/75/100, but that's the way it goes with free equipment.


There is also a possibility that these 'crypto related' machines had a 7.0 unit code, making
them that much more difficult to sneak illegal copies.  For local encoding and decoding work,
the actual operating speed made no difference.  Once a message was encoded, it was transmitted
by other means.  Sometimes by CW and other times by RTTY, at some standard, 'fleet speed' using
a perf tape and a TD.


PLEASE REALIZE THAT THIS IS JUST MY OPINION, BASED ON 50+ year-back experience, and some
more recent knowledge gained about 'special crypto speeds'.   


I hope that if a GreenKeyer gets this machine that it is a standard machine and that it
serves them well for years to come.  If the machine has a 'local loop' and can be powered up
for a potential buyer to 'type and play' with, that will merely prove that the loop is right
and that the print mechanism works.  It could be working at 65 WPM, 7.0 code and 95% of the
users/observers would not likely see the difference.  You almost have to see a machine 
running at 'tape speed' to realize that 'something is not quite right'.


A friend of mine, many years back, built a TTL chip Gear Shift for his station.  He put 100
WPM gears in his 28 and fed the output of the 'gearshift' into the loop.  Running a 60 WPM
signal into the system made a very strange sound from the machine.  Technically, the
'throughput' was 60 WPM, but the machine created each character at 100 WPM and had a very
noticeable 'hesitation' between characters, as opposed to what you would expect at 60 WPM,
'machine speed', when nothing seems to stop moving.


Again, I hope the ultimate buyer ends up with a 60 WPM, 7.42 machine!


73,


Ralph - W8ROI


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