[GreenKeys] [External] Kleinschmidt 7302 ?

[David I. Emery]

On Fri, Jul 29, 2022 at 08:47:56PM +0000, Jones, Douglas W wrote:
> From: Jim Cooper [jim.w2jc at gmail.com] -- Thursday, July 28, 2022 11:42 PM
> 
> > As far as printing, it is VERY unique ... there is a
> > rotating metal drum BEHIND the paper and a hammer
> 

> This is hardly very unique.  About half of the high-speed line
> printers made in the 1960s and 1970s worked this way.  CDC, Digital. and
> several other vendors made 300 line-per-minute printers that printed on
> 132 column paper using one hammer per column and precise timing on the
> print hammers.  Here's a sample of typical printing from such a printer
> (in this case, a CDC line printer from 1974):

	As someone around computers back then (70s) I'd say in my
experience it was considerably more than half of the really seriously
high speed high volume LPRs.   These were not table top units... more
things the size of a Cooper Mini that could chew through a box of fan
folded paper one could barely lift in maybe an hour or less (actually
printing pages of stuff, not just top of page and printing one line).

> -- http://homepage.cs.uiowa.edu/~dwjones/plato/DrumPrinter.jpg
> Aside: I used that sample to illustrate this web page:
> -- http://homepage.cs.uiowa.edu/~dwjones/plato/#printing


> The interesting thing from this sample is the poor horizontal alignment of the letters.  The row of dashes across the top illustrates this best.  I would hope that the Kleinschmidt printer did better, but it wasn't nearly as fast a printer, with one moving hammer instead of a row hammers that all try to bang at once to print each line.

	It varied with the condition and adjustment of the machine.
	
	No printing technology of that era came anywhere close to
the precision and consistent alignment of laser printing... though later
word processor oriented character at a time printers were much closer
to what a superior typewriter could do than fast LPRs.


> The competing approach to high-speed impact printing was one IBM and
> Data Products preferred.

	I was aware of IBM chain printing, but actually used and even owned
medium size Data Products drum printers and one or two larger ones at
work... and I'm not particularly aware they ever made chain printers
then (or maybe later) - but cannot say for certain they didn't.

> 	Instead of a spinning type drum, they had a constantly moving 
> type chain.  On IBMs printers, you could change out the chain to change
> fonts.  The same array of hammers whacked the ribbon against the paper
> against the type chain, but the timing was different because of the
> horizontal scan of the chain past the hammers. >  



> 	The GE Terminet 600 and competitors used a very similar scheme,
> except that instead of a type chain, they had a type rubber band, with
> metal type fingers inserted into the band.

	These were pretty slow compared to real line printers and intended
for desktop type stuff... 

	And it is obviously important on a Teletype list to point out
the infamous Teletype model 40 which used a rubber belt - made of some
substance that had a short lifetime before it turned to goo - with  type
pallets similar to those in 28/35/37 type boxes inserted into holes in
it.   Interesting that the 40 drove the type hammers mechanically with
small solenoids activating a pawl that grabbed a spinning bail and the
energy from the motor driven bail being what banged the type pallet into
the ribbon and paper.   This was in contrast to the chain and drum
printers which took enormous power supplies and high power switching
circuits that discharged a capacitor into each of the  hammer solenoids
at the right instant to print a character as it went by on the drum or
chain.

>  	 Those were fun because you could use long-nose pliers to pull out
> the type fingers and move them around if you wanted, for example, to
> swap the slashed and unslashed versions of O, depending on which one you
> wanted to be zero and which one you wanted to be oh.  There's a sample
> of GE Terminet output on the above cited web page as well.

	There certainly was a big advantage to chain printers in
flexibility of character sets... and the ability to equip a particular
one with some odd additional characters (foreign language for example)
without having to replace a costly precision type drum.   And some kinds
of accidents could trash a type drum, while chains and the type elements
on them were lots cheaper and easier to replace.

-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."