US Robotics USR3520 User Manual page 82

Gateway
(DCE)
Connect the Gateway with another DCE device (modem, PLC,...)
In order to connect the gateway to another DCE device you should use a cross cable. (= null modem
cable).
Industrial Serial Card Specifications
Specifications:
RS232

One RS-232 serial port, 921.6 Kbaud maximum speed

The RS232 interface on the industrial serial card is identical to the one on the low cost serial card.
Please have a look at this
Revision: 1.00
low cost serial card for more info on the RS232 interface.
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