[GreenKeys] sticky bits - 8 level code

[Jim Haynes]

I'm sure I've told this story before, but maybe it will bear repeating.

At first Teletype didn't know how to make a parity keyboard, so early
Model 35s made the 8th bit always marking.  (An aside: I'd say the problem
was because of trying to shoehorn all the necessary stuff into what was
originally a Model 28 keyboard, instead of designing an all-new model.)

After the parity keyboards came into service there were complaints about
parity errors in the transmitted signals.  When transmitting from tape the
8th bit sometimes came up marking when it should have been spacing.  I'm
not sure which tape reader was involved - probably the LXD.  This was
discussed with the designers of the reader.  They said they had a lot of
trouble at 110 baud getting the parts settled down when it was time to
transmit the 8th bit.  Since the 8th bit was always marking they built
in some bias to cause it to go marking if there was any uncertainty.

This is a completely apocryphal story.  There's probably no one living
who can confirm or deny.

 	---

 	"Ya can argue all ya wanna, but it's dif'rent than it was."
 	"No it ain't! No it ain't!  But ya gotta know the territory."
 		Meredith Willson, The Music Man