Tables A-1 and A-2 list the signals and names for RS-449 and X.21 circuits.
Table A-1 RS-449 Signals
Circuit |
Name |
Direction |
---|---|---|
SD |
Send Data |
To DCE |
RD |
Receive Data |
From DCE |
TT |
Terminal Timing |
To DCE |
ST |
Send Timing |
From DCE |
RT |
Receive Timing |
From DCE |
RS |
Request to Send |
To DCE |
CS |
Clear to Send |
From DCE |
RR |
Receiver Ready |
From DCE |
TR |
Terminal Ready |
To DCE |
DM |
Data Mode |
From DCE |
SG |
Signal Ground |
|
Table A-2 X.21 Signals
Circuit |
Name |
Direction |
---|---|---|
G |
Signal Ground |
|
T |
Transmit |
To DCE |
R |
Receive |
From DCE |
C |
Control |
To DCE |
I |
Indication |
From DCE |
S |
Signal Element Timing |
From DCE |
B |
Byte Timing |
From DCE |
The diagram below illustrates the pin connections required for an X.21-to-RS-449 converter.