Archiving Data Permanently

[Fritz Whittington]

On or about 2005-08-24 12:29, Tim whipped out a trusty #2 pencil and 
scribbled:

>On Thu, 2005-08-25 at 01:49 +0930, Tim wrote:
>
>  
>
>>I think that the old paper punch cards are about the only technology
>>that lends itself to you building something to read them long after the
>>original readers start working.
>>    
>>
>
>Of course that should say after they "stop" working.  :-\
>
>  
>
Actually, I think paper tape is much easier than punched cards, if you 
have any significant volume of data.   In 1977, I designed and built a 
gadget that read paper tape a lot faster than the Teletype could, and 
I'm a software engineer, not a hardware designer!   What makes paper 
tape so easy is that the sprocket hole gives you a positive indication 
that a set of holes is ready to be sensed at a fairly precise offset 
distance away.  Nine teeny light sensors mounted in the proper pattern, 
and nine input bits on the computer to read them.  Didn't matter if you 
pulled the tape through at any particular speed (as long as it wasn't 
too fast for the computer software).  The sensor on the sprocket holes 
generated an interrupt, the software read the other 8 sensors and put 
the bits into memory, then went to sleep until the next interupt.  
Worked like a champ, even on a 2 MHz Z-80...

-- 
Fritz Whittington
"I was gratified to be able to answer promptly, and I did.  I said I didn't know." -- Mark Twain 

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