[GreenKeys] Handling CRs

[Jerry Murphy]

The standard M28 typing unit is capable of causing a CR function from any
function bar installed in slots 4 or 5.  Look for the 150377 Arm.  It is
installed on the 162729 Guide Bar.  It spans stuntbox slots 4 and 5.  The
same idea goes for stuntbox slots 39 and 40.  Any function bar installed
there will cause a line feed.  Look for the 162728 Arm.  It spans stuntbox
slots 39 and 40.  The 152359 arm was optional and it spanned slots 39, 40 
and 41.  It was used on some form-out and vertical tab installations.

The purpose of the LF function bar in slot 38 was to suppress spacing on
LF.  If I remember correctly, there was little margin for correct operation
of space suppression when a LF was received and single line-feed was selected.
So, the decision was made to off load the space suppression job from slot
40 and move it elsewhere.  Slot 38 is the normal place but it could go in
any unused slot.  

Replicating a CR function bar and installing it in slot 40 will give you a
CR and a LF every time a CR is received.  This will cause all printed material
to be double spaced even though the single-double LF lever is in the single 
position.

Teletype came up with the 193936 Mod Kit to solve the overline and the double 
or triple line feed issue.  The 193936 mod kit is a stunt box modification that 
causes a CR and a LF on the receipt of the first CR and then suppresses the next 
two line feeds.  It was installed with the ACRLF modification.  So, a sequence 
of CR-CR-LF would generate a carriage return and one line feed.

Teletype did make special stunt box function pawls that would operate the 
function lever in the next higher numbered slot.  The 193936 mod kit makes use
of these pawls.  These pawls are in the parts book as pawls 153604 and 153598.
In the parts book, they look identical to the common 152653 function pawl but
they are different. The 153604 pawl has a long arm which extends to the next 
higher numbered slot.  The 153598 slot has a reduced clearance arm which makes 
space for the long arm on the 153604 pawl.  Operation of a function bar that 
engages the 153604 function pawl will simultaneously operate the function lever 
associated with the 153604 pawl and the function lever in the next higher 
numbered slot.  

Jerry Murphy




-----Original Message-----
>From: Eric NO3M <no3m at no3m.net>
>Sent: Sep 1, 2017 10:43 AM
>To: greenkeys at mailman.qth.net
>Subject: Re: [GreenKeys] Handling CRs
>
>I performed the M28 non-overline "no parts" mod for emulating a CRLF 
>when an LF is received according to the SMECC site.  My machine was a 
>bit different, there was no LF function bar, etc., in slot 38, but 
>rather one was installed in slot 42 (bar label "LF"), which appears to 
>be the "form out" slot.  What is the actual mechanical operation of 
>"form out" in a M28?
>
>I swapped the "CR" function bar (slot 5) and "LF" function bar (slot 42) 
>and the mod works as advertised, a received CR results in no action 
>(slot 42 -> form out?) and a received LF results in a combined CR+LF.  
>The "SC LF" labeled function bar was left alone in slot 40.
>
>Since CRs are the prevalent characters being sent, I'd like to actually 
>try modifying the CR behavior to be a CR-LF combination, and make LF a 
>no action character.  There appears to be several universal function 
>bars in slots 25-28 (Bell UC S, Busy Light/Interruptor, Copylight), 
>spares?  If they are in fact spares, I assume I could snap tines off to 
>replicate the original "CR" function bar, and install it and the 
>original CR function bars in slots 5 and 40?
>
>The machine has the auto CR-LF mod installed, with "CR LF" labeled 
>function bars, etc., installed in slots 4 and 39.  Since those slots 
>don't appear to have any assigned function, I assume they are special 
>bars designed to engage the slot next to them (ie. slot 5 = CR and slot 
>40 = LF)?
>
>Thanks for any insight.
>
>73 Eric NO3M
>
>