Can the firmware be updated on the AC4490/CL4490 or AC4790/CL4790 in the field?
Unfortunately, no. The AC4490/CL4490 and AC4790/CL4790 can only be upgraded using a special tester (programming) device. However, radios should ship with the most current (stable) version, as there have not been any updates to the firmware for many years.
Other variations in firmware, indicated by the -01, -02, -03 included in the part number are regionally significant, and must be purchased with the correct firmware version for the region the radio will be deployed. The regional firmware versions cannot be interchanged on the radios. Please see FAQ: What is difference between AC4490/AC4790 product part numbers that end with -01, -02, -03? for additional information on the regional variants.
Note: if the part number does not include a -xx then it is loaded with the FCC/IC (-01) firmware.