cctech Digest, Vol 80, Issue 1

M H Stein dm561 at
Thu Apr 1 13:34:43 CDT 2010

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

> 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?



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.


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