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Terminal To Modem (or DCE Host)
Refer to the diagram below to understand why a null modem adapter may be needed when connecting the AUX
serial port to a modem or a DCE host. The EIA port will connect directly without a null modem since it is a DTE
device.
Terminal To Host (DTE) OR Printer
Refer to the diagram below to understand why a null modem adapter may be needed when connecting the EIA
serial port to a serial printer or a host port without a modem (most hosts and serial printers are DTE devices).
The AUX port will connect directly without a null modem since it is a DCE device.
