[GreenKeys] Fw: TeleType Model 33 Not Sending Some Control Characters Correctly

[Robert Laag]

PROBABLY NOT RELATED BUT YEARS AGO I WAS SURPRISED WHEN I GOT A COUPLE OF 35 TELETYPES AND THE KEYBOARDS WERE FROM AN EARLY VINTAGE THAT DIDN'T HAVE CERTAIN KEYS...  I HAD TO REPLACE A COUPLE OF BARS UNDER THE KEYBOARD AND THEN ADD MAYBE THE CTRL KEY AND ANOTHER POSSIBLY...  GUESS THE ASCII CONFIG CHANGED IN 1968 OR SOMETHING...  AS I SAID, PROBABLY NOT RELATED BUT HAD TO DO THIS TO A COUPLE OF MY MACHINES...  BOB

----- Forwarded Message -----
From: Robert Jarratt <robert.jarratt at ntlworld.com>
To: greenkeys at mailman.qth.net 
Sent: Saturday, October 26, 2013 2:24 PM
Subject: Re: [GreenKeys] TeleType Model 33 Not Sending Some Control Characters Correctly
 


I have had two replies on this and finally got a chance to look at it today. I was asked if I had moved the machine, while the answer is yes, the problem had started before I moved it.
 
I have been looking at the manual and at my machine and I am slightly confused. I believe I have a parity keyboard. The manual 574-121-100TC in Fig. 10 shows a set of contact wires at the left and the right that are operated by the CTRL key.
 
However, on my keyboard there are no contact wires on the right (as you look from the front) operated by the CTRL key, nor is there room for any; it doesn’t look as if anything is missing or broken either. In fact if that was the case then it would not work with any letter keys at all, but the reality is that it works correctly for some keys but not all of them.
 
From what I can see, the operation of the CTRL key is always the same. It changes the contact wires on the left of the keyboard regardless of what letter key I press at the same time, and on the right it has no effect at all on the contact wires. So I don’t get why sometimes it seems to work and other times it doesn’t.
 
Regards
 
Rob
 
From:Robert Jarratt [mailto:robert.jarratt at ntlworld.com] 
Sent: 21 October 2013 22:15
To: greenkeys at mailman.qth.net
Subject: TeleType Model 33 Not Sending Some Control Characters Correctly
 
My Model 33 had been working perfectly. But for some reason it has started not to send some characters to the computer correctly.
 
For some reason CTRL-C (ASCII 3) is sent as “C” (ASCII 43 in hex). For what I need it for this is disastrous because it is the character I need to send to start the login sequence on the simulated computer that I need it to log in to. I have checked all the CTRL keys, the ones that don’t work are CTRL-C, CTRL-E, CTRL-F, CTRL-I, CTRL-J, CTRL-L, CTRL-O, CTRL-Q,  CTRL-R, CTRL-T, CTRL-W, CTRL-X, in each case hex 40 is added (ie bit 7 is set). It does not even seem to be a parity issue because contiguous characters are sent incorrectly.
 
Ordinary letters are sent correctly.
 
Any ideas where to start looking?
 
Regards
 
Rob
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