HP iPAQ h5400 Series Reference Manual page 25

Getting Started
7. If you have not already done so, connect either the (a) serial
or the (b) USB connector (NOT BOTH) on the universal
cradle to the port on the back or front of your personal
computer.
✎
Connect either the serial or the USB connector. Do not connect
both connectors at the same time.
✎
Use the USB connection for faster performance. Microsoft
Windows NT users must use the serial connection.
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