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Bringing the Model 33 to the 21st Century - Part 10


Veteran Member
Oct 22, 2008
Kamloops, BC, Canada

Finally after almost two and a half years of work, 32 lines of code and 12 pages of diagrams it was finished. The first CCU for a model 33 designed exclusively to control a Hayes Smartmodem hidden away inside the stand while looking completely original, being completely modular AND bridging the gap from the early telecommunicating days to the modern era was completed.







The proper teletype stand provides a better location for mounting all the external components out of view, plus a place for me to hide the documentation for the teletype, the modem and the schematics for the CCU.


Now….to test it.

As mentioned before there are limitations brought on by the modern DSP/WinModem modems which have no idea how to work below 300 baud. Likewise most operating systems now assume that 300 baud is the slowest anyone will want to go unless you explicatively make it work with a third party application or workaround, so you run into instances where the hardware might handle it but at least without heavy in-depth knowledge on how you can force rates on the UART the OS will not allow it.
For testing I proposed using a Silicon Graphics O2 with a modem hanging off its serial port and Irix set to deliver a console on the same port and expect an ASR33 using the terminfo file Irix itself included. Of course, by default Irix would not let you specify below 300 baud and that I’ve been able to try so far, forcing 110 was not working, so testing was performed instead by calling my buddy “Fink” in Toronto who used a modem and a laptop running HyperTerminal and a physical serial port modem to communicate with me and remotely activate my paper tape reader and send him a message.
If I could get Irix to behave with the serial port (which I KNOW will support 110 baud), sure there’s a few good videos I could make out of that demonstrating how this works, otherwise plan B is to build a little buffer that sits between the modem and the serial connection to the current loop adapter and slows all incoming 300 baud data down to what the Teletype expects which would then mean that regardless of what modem the other end uses, the teletype will communicate with everything.

I am quite excited on how this project turned out. It looks fantastic, it runs fantastic and I ended up putting a very large amount of my skills into this from fabrication to the actual circuit design. Now not all of this work was possible on my own. I’d like to take this moment to thank Ddrl46, Chryseus and Nikomo on the Facepunch forums for a lot of the hair pulling electrical assistance and programming help, the folks at the Classic Rotary Phones forum for their telephone assistance, Connor Krukosky for the stand, Fink for the remote teletype session from his place in Toronto and Ross for selling me the teletype in the first place.

I would also like to point out to our our blog and website administrator, EvanK, that I repeatedly told you six months ago that the max size we can make a blog posting is far too small. Don't even try calling me out for spamming the blog. :U