[GreenKeys] ASR33 Computer Terminal

[cswiger]

Gang -

	Interfacing the model 33 (3300, 3310 and 3320 series -
wiring diagrams here:

http://www.pdp8.net/pdp8cgi/query_docs/view.pl?id=240 )

just got very simple, if your model 33 is wired for full
duplex. All you need is a 68 ohm and a 1k ohm resistor
and two 9 volt batteries. Wire your pc or notebook rs232 TD
(pin 2 for 25 pin, pin 3 for 9 pin, oddly enough) thru a
68 ohm to P2 pin 8 in the tty, and P2 pin 7 to rs232
SGND (pin 7 for 25 pin, 5 for 9 pin). That drives transistor
Q1 on page FS-1 in the above diagrams. It prints for me.
For the keyboard, connect either tty P2 pin 5 or 6 to your RD
(pin 3 for 25 pin, 2 for 9 pin) and also to a 1k resistor. The
other end of the 1k resistor goes to the positive end of the two
batteries connected in series, and connect the middle of the
two batteries to SGND. The Negative end of the two batteries
goes to the other keyboard P2 pin 5 or 6 not used above. While
marking your RD gets negative 9v thru the keyboard contacts.
During a space (open) pulse it gets positive 9v thru the 1k
resistor. Larger then 1k may work and give better battery life.

--Chuck