Pixels of the Edge

[Kevin Arnold]

Here's a question only a true techie could appreciate. I notice on my RCA 38" direct view that along each edge of the tube is a small area midway along the edge (which is opaque) where one or two pixels are uncovered i.e. a small dot at the 4 midpoints. I looked at two larger NTSC TV's that I have and see the same thing. So this is obviously not a flaw but is intentional. Why? Does this serve a purpose? For alignment and/or overscan. I know its a minor nit picky thing but gotta know why.

[borghe]

I believe it is a basis for centering. You should be able to take any test pattern that extends a center line out and use it for a mark. Not positive but I thought that's what it was for.