Modemulator User Guide
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Appendix J: DB9 Pinouts
The USR3520/USR803520 has two DB9 serial ports.
Terminal Port
The USR3520/803520 Terminal port is an RS-232 DCE presented on a DB9 female connector using a
standard pinout.
RS-232 output signal levels are nominally ±5v.
Modem Port
The USR3520/803520 Modem port is an RS-232 DTE presented on a DB9 male connector using a standard
pinout.
RS-232 output signal levels are nominally ±5v.
DB9F Pin Symbol
Description
Direction
1
DCD
Carrier Detect
Output
2
TXD
Transmit Data
Output
3
RXD
Receive Data
Input
4
DTR
Data Terminal Ready
Input
5
GND
Ground
-
6
DSR
Data Set Ready
Output
7
CTS
Clear To Send
Input
8
RTS
Request To Send
Output
9
RI
Ring Indicator
Output
DB9M Pin Symbol
Description
Direction
1
DCD
Carrier Detect
Input
2
RXD
Receive Data
Input
3
TXD
Transmit Data
Output
4
DTR
Data Terminal Ready
Output
5
GND
Ground
-
6
DSR
Data Set Ready
Input
7
RTS
Request To Send
Output
8
CTS
Clear To Send
Input
9
RI
Ring Indicator
Input
