[GreenKeys] USB interface for 5-level machines

[Jim Haynes]

Looks like it is slightly more elaborate than that, as he says it is
emulating the Telex current loop interface.  Which involves polarity
reversal and dialing the number and that sort of stuff.

 	---

 	"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