RCA COSMAC Operator's Manual page 82

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APPENDIX C
TTY-MODEM-MICROKIT SWITCHBOX
A user who has a Teletype connected to a modem as a
timesharing terminal may share the same Teletype with
the Microkit by connection through a user-wired switch-
box as shown in Fig. 22 below. The three normal modes
of operation of the switchbox are:
1. Connect TTY to Microkit for stand-alone operation.
2. Connect modem output to Microkit for program load
from timesharing.
3. Connect TTY to modem for timesharing.
Some modems connect to the TTY through the terminal strip
(position 3-4 and 6-7) as shown in Figure,20, Appendix A.
Others may connect through a MOLEX jack to 32 (the same
receptacle needed for the Microkit). In either case,
isolate the two current loops, one to the keyboard (SEND)
and one to the printer (RECEIVE) and bring out as four
wires. The TTY cable, supplied with the Microkit (see
Note 1, Fig. 21), can be cut to produce two 4-wire cables.
The three-way routing of signals can then be accomplished
by means of a switchbox, wired as shown in Fig. 22.*
TTY "CSDP lOAD"
TO ON OFF
KIT
-
lSTAND-
AlONE
MODEM
2TIME-
3
TIME -
SHARINGSHARING
LOAD I '
*
An alternative implementation is
to use a 3-position, 7-pole rotary
switch, as sketched here.
TIMESHARING
LOAD
o
- 77 -
TTY-KIT TTY-
TIMESHARING
o