newRPL devices can communicate with newRPL Desktop by connecting the calculator to the host with a USB cable. There's some additional steps needed on various operating systems in order to communicate with the calculator:

Windows

No additional steps needed, just plug it.

Linux

The current user (the user newRPL Desktop is running as) needs to have read/write permissions to USB devices. Create a new group usbdevices, then add the current user to that group. Next, create a file (as root) /etc/udev/rules.d/50-HIDDevices.rules, containing the following two lines:

KERNEL=="hidraw*", SUBSYSTEM=="hidraw", MODE="0664", GROUP="usbdevices"
SUBSYSTEM=="usb", ATTR{bInterfaceClass}=="03", MODE="0664", GROUP="usbdevices"

This will indicate the system to assign the group usbdevices to all new HID devices, and permits read/write to members of that group. Finally, restart the system for the new permissions to take effect.

freeBSD

The current user (the user newRPL Desktop is running as) needs to have read/write permissions to USB devices. Create a new group usbdevices, then add the current user to that group. Next, create a file (as root) /etc/devfs.rules, containing the following:

[localrules=5]
add path 'ugen*' mode 0660 group usbdevices
add path 'usb/*' mode 0660 group usbdevices
add path 'uhid*' mode 0660 group usbdevices

Edit the file (as root) /etc/rc.conf and add a line at the end:

devfs_system_ruleset="localrules"

Finally, restart the system for the new permissions to take effect.