[GreenKeys] Teletype and TEMPEST info

[Jim Haynes]

There's also an article I can't find right now about how the Soviets
intercepted shipments of Selectric typewriters to the U.S. Embassy
and fitted them with little radio transmitters.  The Selectric lends
itself to this treatment because, like a teleprinter, it encodes the
keyboard characters into a six-bit code that controls the printing
mechanism.