Terminal To Modem (Dce) Or Host; Terminal To Host (Dte) Or Printer - IBM InfoWindow II 3153 User Manual

Introduction

Terminal to Modem (DCE) or Host

Refer to the diagram below to understand why a null modem adapter may
be needed when connecting the second serial port (SES2-AUX) to a modem
or a DCE host. The first host will connect directly without a null modem
since it is a DTE device.
SES1 EIA
DTE
pin2
Transmit
pin3
Receive
pin20
DTR
pin6
DSR

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.
12
Host
SES2 AUX
D
Modem
C
E
DCE
pin2
Transmit Receive
pin3
Receive Transmit
pin20
DTR DTR
pin6
DSR DSR
Host
D
Modem
C
E
pin2 pin2
Transmit
pin3 pin3
Receive
pin20
pin20
DTR
pin6 pin6
DSR