When is high not high.

From: Chris W (1qazse4_at_cox.net)
Date: 02/19/05 

Date: Fri, 18 Feb 2005 21:22:05 -0600

I have my inventory of stuff I got on that ebay auction so I decided to
build something and see if it would work. I think I learned something,
but I'm not sure exactly what and was hoping some one could tell me. I
took my MH7442, a 10 LED bar thing-a-majig, a set of dip switches and a
resistor. Wired it up to display the LED 0 through 9, based on the
Binary input from the dip switch. At first it didn't work. After some
experimenting, I found what I thought was a high going into th BCD input
of the MH7442 was not what it wanted. I had the switch set up so a low
was the absence of a voltage source, what it really wanted, was that a
high was the absence of a ground connection. My question is, is there
some way I could have known this? Is there something in the data ***
that would tell me that? 

-- 
Chris W
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