[GreenKeys] physical tape format question

[Jim Haynes]

It's a fine question, and an interesting one.

The hole spacing is the same for tapes from 5 to 8 level: 10 per inch.
However 6-level is funny in one respect.  In all the others the center
line through the feed holes is also the center line through the code
holes.  But in 6-level the leading edge of the feed holes lines
up with the leading edge of the code holes, so the centers are not
in line.  This is called "advanced feed holes".  But usually tolerances
are such that you can read 6-level advanced feed hole tape on an
inline-feed-hole reader, and 6-level tape punched with inline feed
holes may be perfectly readable on a reader designed for advanced
feed holes.  In fact it should not be hard to adjust a reader to
expect advanced feed holes.  What's hard is punching them, since
if all the punches are in the same punch block you need a special
punch block.  I guess there is some equipment that punches the feed
holes separately; and that would allow adjustment to either standard.

I have no idea why it was done this way - it just was.



jhhaynes at earthlink dot net