New subject: Documation card readers (was Re: cctech Digest, Vol 80, Issue 1)

1 Apr 2010

-------------Original Message:
Message: 27
Date: Thu, 1 Apr 2010 00:39:06 -0400
From: Dave McGuire <mcguire at neurotica.com>
Subject: Re: Reading ancient paper digital media (was Re: Hamurabi
	Focal	source)

<snip>
...
  The way my reader (A Documation
 M200) does it is to move the card at constant speed using known-diamter
 rollers, then to detect the leading edge of the card (basically when the
 optical sensors g form all on to all off, then use that to produce an 
 internal clock signal that should align with the centres of the columns 
 (if you see what I mean) and us that to strobe the read logic. 
  What if the card slips?

           -Dave

--------------Reply:

Some readers used a blade that caught the edge of the card and pushed
it through just as the parallel-read IBM EAMs had done in the old days;
no problem with slippage, it either fed correctly or jammed.

mike