[GreenKeys] shockingly basic question - Teletype Model 33 ASR

Thu Feb 4 15:29:48 EST 2021

OK well this is all very embarrassing. I have two almost identical
teletypes (both non-parity) .... the other one works great connected to my
Terminal Server so thought I'd better  swap the RS232 Adapters, port and
cable.. and hey presto - my "not working due to parity errors" Teletype
started running fine!

I then swapped back to the original Adapter, cables and port... expecting
things to NOT work... but of course, everything ran fine.

I've tried jiggling the cables (I was hopeful maybe a weird cable problem
could be the issue) but I am struggling to see how a wiring problem would
look like a legit parity problem.

Anyway! All good for now.. but I am curious what would cause these
parity-like symptoms. I am going to replace the cables anyway, and probably
grab another converter just in case.

cheers!
Andy

On Wed, Feb 3, 2021 at 11:05 PM Mike Douglas <deramp5113 at yahoo.com> wrote:

> Since you are concerned about the parity of your keyboard while testing
> the TTY printing function, I assume your terminal server is in a mode where
> it echos characters that you type on the TTY keyboard back out to the TTY
> printer and you are testing your printer by typing on the TTY keyboard?
>
> If this is what you’re doing and you have a non-parity keyboard, then set
> the serial port to 7 data bits plus mark parity (non parity keyboards set
> the 8th bit to one). This should ensure the server accepts the typed
> characters. If you type one character at a time with a short pause between
> each character, then each character should echo properly to the TTY
> printer. The pause between each character will be more than the two stop
> bits the printer requires (and the printer ignores the 8th bit).
>
> If, however, you have a telnet session open and are sending data from a
> remote device to the TTY printer and are not using the TTY keyboard to
> generate test data, then set the serial port to 8 data bits plus mark
> parity. This will appear as 8 data bits and 2 stop bits to the printer (as
> it requires) and the printer can then keep up with a steady stream of data.
>
> If you are getting some garbage characters with either of these methods
> but everything prints correctly in local mode, you made need to adjust the
> rangefinder a bit.
>
> Mike
>
> On Feb 3, 2021, at 9:22 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
>
> 
> My Teletype has a Deramp converter which goes direct into an Equinox
> ELS-16 terminal server.  When I start I get a session with the terminal
> server and can interact directly with the server ... or telnet onwards
> elsewhere.
>
> On Feb 3, 2021, at 10:00 PM, Mike Douglas <deramp5113 at yahoo.com> wrote:
>
> 
> I guess I’m confused as to your test setup then. What is sending data to
> your Teletype? Is it coming from an external source other than the
> Teletype, or are you testing by somehow looping keyboard input from your
> TTY back out to the TTY printer?
>
> Mike
>
> On Feb 3, 2021, at 8:36 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
>
> 
> I think I am still missing a trick or two here...I tried every combination
> of 8 and 7 even/odd/none/mark/space and I get no printing at all with 8
> bit, but moderately bad spelling errors with 7.  See attachment below...
> presumably this means I have the non-parity keyboard?
>
> thanks in advance for your thoughts!
> Andy
>
> On Sun, Jan 31, 2021 at 8:18 PM Mike Douglas <deramp5113 at yahoo.com> wrote:
>
>> If you select 8 bit with mark parity on your terminal server, you’ll
>> probably get the 8N2 timing the Teletype requires (the mark parity bit
>> serves as the first stop bit).
>>
>> Mike
>>
>> On Jan 31, 2021, at 7:11 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
>>
>> 
>> Thanks guys for the responses - a lot of great info for me to digest!
>>
>> My terminal server (Equinox ELS-16) allows me to define character size as
>> 7 or 8 bits, and to set parity as NONE, ODD, EVEN, MARK or SPACE.
>>
>> I don't seem to have the ability to specifically state the number of stop
>> bits, however.
>>
>> Anyway.. I'm going to crack my Teletype open and confirm exactly what's
>> going on.
>> cheers!
>> Andy
>>
>> On Sun, Jan 31, 2021 at 5:43 PM Keith Lueck <kwlueck at swbell.net> wrote:
>>
>>> Jim & Wayne are spot-on, of course.  I learned the hard way that you
>>> best include the parity bit - even though the 33 doesn't give a whit about
>>> parity...
>>> My machine was occasionally producing errors when I was feeding it 7 N
>>> 2.  Wayne Durkee set me straight, and, viola, when I sent it 7 M 2,
>>> everything was 100% ducky.
>>>
>>> On Sunday, January 31, 2021, 03:32:30 PM CST, Jim Haynes <
>>> jhhaynes at earthlink.net> wrote:
>>>
>>>
>>> All the 33s and 35s generate 11 unit code.  1 start bit, 7 data bits, one
>>> bit which may be even parity or may be marking, and two stop bits.
>>> That's
>>> where 110 baud comes from. 100 wpm = 10 chars/sec and each char contains
>>> 11 bits.  The reason for two stop bits is the difficulty of making a
>>> mechanical selector that is reliable at 100 wpm.
>>>
>>>     ---
>>>
>>>     "Ya can argue all ya wanna, but it's dif'rent than it was."
>>>     "No it ain't! No it ain't!  But ya gotta know the territory."
>>>         Meredith Willson, The Music Man
>>>
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>>
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>>
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>>
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>>
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>> <non parity keyboard.png>
>
>
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