The 124-25d.JA2 portion of the string identifies the specific release version (12.4(25d)JA2), which includes various stability fixes and feature updates for older Aironet hardware. Why Convert to Autonomous Mode?
Download the .tar image from the Cisco Software Central (requires a valid contract) and set up a TFTP server on your computer. C1240 K9w7 Tar 124 25d Ja2 Tar 26
Cisco access points generally run one of two types of firmware: The 124-25d
Ensure the file on your TFTP server matches the name the AP is searching for exactly. C1240 K9w7 Tar 124 25d Ja2 Tar 26