[GreenKeys] Wrong cam on model 15

[Jim Haynes]

You can read a lot of hand-waving stuff about the holding magnet selector
being more sensitive, which I guess it is.  But the reason for it,
according to the inventor, was in connection with TWX cord switchboards.
This was from Walt Zenner, who was VP for R&D at Teletype for many years.

The pulling magnet selector canonically required a 120 Volt loop.  In
TWX switchbords this voltage appeared at the exposed switchboard cord
tip and was dangerous to the switchboard operators.  The holding magnet
selector could be used satisfactorily in a 48 Volt loop.  That voltage
was already being used on voice switchboard cords, so at least it made
the probability of getting killed at the TWX switchboard no greater than
what it was at a voice switchboard.



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 	"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