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_________________________________________________________________ 81
Appendix B -
Instructions for Converting a Model 33 Teletype Terminal
from Half-to-Full-Duplex Operation and from
60-mA to 20-mA Operation
For a Teletype terminal connected for half-duplex
operation, the following modifications can be made to
convert it to full-duplex operation.
I. Locate the black terminal strip in the back. See
E·
i
g.
Bl.
2. Move the
brown/
yellow and white/blue wires from
pins 3 or 4 to pin 5.
-For Teletype terminals, connected for 60-mA
operation, the following modifications can be made
for 20-mA
operation.
1. Move the violet wire from pin 8 to pin 9.
CURRENT-
LIMITING
RESISTOR
MODE
SWITCH
KEYBOARD
IE]
~=======:
PRINTER
c::::=::J
TERMINAL STRIP
92CS
-
28 10
4
2. Move the blue wire connected to the current source
resistor (a flat green resistor with four tabs located to
the right of the keyboard) from the 750-ohm tab to the
1450-ohm tab.
Fig. B2 gives the detailed interface circuitry
between the CDS logic signals and the pin con-
nections for the Teletype terminal in the full-duplex
mode. Note particularly the isolation of the two
Teletype (TTY) current loops. Also shown in Fig. B-2
is the detailed interface circuitry between the CDS
logic signals and the pin connections for an EIA
RS232C type data terminal.
SEND
RECEIVE
WHTI
BRNI
BLU
YEL
VIOLET
TERMINAL
STRIP
92CS-28
1
0
5
Fig,
81 - Location of and connections to terminal strip for Model 33 Teletype
data terminal showing connections for 20-mA full-duplex
operation.
EF4-N
SELO-P
N-7-P
MRD-N
DBO-P
CD4049
OUTPUT
DECODE
AND
LATCH
CA324
+12V
R4
+12
V~
>t-------,
470 a
J'-Zf'
8)
b
~R.f.}'1
_
KEY BOARD
r-----~----~--~
R5
JI-4
470n
L-----+-0-5
V
10 kn
.--"'V'w'V--o
+
5 V
4 .3kn
J2~
}
FROM EIA
TERMINAL
.,,£0 J2:1,~
TO TTY
PRINTER
DATA
>-_______________
~
>=-----<
TO EI A
J2-3
TERMINAL
-5
V
R9
DATA SET READY
+12V~)±..-...<
CLEAR TOSEND
560 n
J2-6,7, 8
DATA CARRI ER DETECT
92CM-29393RI
Fig. 82 - Detail of CPU- Terminal Interface (See Appendix DJ
_
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