User`s guide

Terminal to Modem (DCE) or Host
Refer to the diagram below to understand why you may need a null modem adapter when connecting the second serial port (SES2-AUX) to a modem or a DCE
host. The first host connects directly without a null modem since it is a DTE device.
DTE
S
E
S
1 EIA
Modem
Transmit
Receive
DTR
DSR
Transmit
Receive
DTR
DSR
pin2
pin3
pin20
pin6
pin2
pin3
pin20
pin6
D
C
E
H
ost
DCE
S
E
S
2 A
U
X
Modem
D
C
E
H
ost
Receive
Transmit
DTR
DSR
Transmit
Receive
DTR
DSR
pin2
pin3
pin20
pin6
pin2
pin3
pin20
pin6
Terminal to Host (DTE) or Printer
Refer to the diagram below to understand why a null modem adapter may be needed when connecting the first serial port (SES1-EIA) to a host port without a
modem (most serial printers are DTE devices and most hosts are not). The second port (AUX) will connect directly, without a null modem, since it is a DCE
device.
DCE
SES2 AUX
Receive
Transmit
DTR
DSR
Transmit
Receive
DTR
DSR
pin2
pin3
pin20
pin6
pin2
pin3
pin20
pin6
D
T
E
Host
DTE
SES1 EIA
D
T
E
Host
Transmit
Receive
DTR
DSR
Transmit
Receive
DTR
DSR
pin2
pin3
pin20
pin6
pin2
pin3
pin20
pin6
Serial
Printer
Serial
Printer
9