[GreenKeys] Introduction - And Looking for Sagem TX20 information

[Don Robert House]

Malcolm,

I do not think we have many Greenkeyers here in the States with the  
experience you need.  However, the list members in the Britain and  
Germany may be able to help.
Of course the time difference may slow a reply.

Good luck,

Don - K9TTY
Currently in Ringwood, Illinois USA
US Central Daylight Time Zone


On 25 May 2008, at 9:46 PM, Malcolm Macleod wrote:

Greetings,



I am new to your list.  It is great to see such an active list for these
lovely old machines.



I have a couple of old teleprinters (Models 15 and 100) put away for  
future
restoration, but my short-term project involves a Sagem TX20 Telex  
machine I
acquired here recently in Melbourne, Australia.  I am interested in  
driving
it with a microcontroller board to effectively create a telex simulator
(basically a simulator that can exchange messages between the TX20 and a
locally-connected PC).  I want the simulator to be capable of
generating/decoding the original dialing, negotiation and answer-back
protocols etc, as well as the exchange of data.



My first challenge though is getting information about both the  
interfacing
_and_ day-to-day use of the TX20.  Does anyone know of any relevant
resources that may be available on the web relating either  
specifically to
the TX20, or to the FSK/PSTN telex interface generally?  If possible, my
plan is to build an interface that connects directly to the TX20's modem
(possibly using an old PC external modem in a direct-connect loop?).  If
that is technically too complicated, I am hoping it might be possible to
connect to a current-loop interface within the TX20 (if it exists!).



Any thoughts? In particular, are the Telex mark/space frequencies  
compatible
with those used in PC external modems?  If they are not compatible, how
complicated is it to decode the frequencies by using a PLL detector  
driven
from a 600 ohm isolation transformer on a local loop?



Malcolm.



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