[GreenKeys] ST-6 SELCAL?

[Eugene Hertz]

I was reading through an Irv Hoff article on troubleshooting the ST6 and the last paragraph he mentions, 

"Incidentally, Sel-cal devices (3) attach to the ST-6 with only a 10k resistor and a silicon diode. Since only a few dozen of the Selcal units have been built, write to me if you need that information."

The reference (3) is:

"3. W. Mallock WA8PCK, and T. Lamb, K8ERV, "The Selcal ? An RTTY Character Recognizer," 73, May, 1968, p. 58."

Anyone have a copy of this article? Might be neat!
Thanks
Eugene