Firmware during the installation
In some cases the installer detects the need for non-free firmware and prompts the user to make the firmware available to the installer to complete the installation, see ipw2200 for an example. In other cases, it does not (601475).
Before starting the installation process on hardware unfamiliar to you, a suggestion is to download the firmware tarball for your installation and have it available on removable storage. When the installer starts, it will automatically find the firmware tarball on the removable storage and, if needed, install the firmware for your hardware. The link to the firmware download for your Debian version is cdimage.debian.org/cdimage/unofficial/non-free/firmware/.
