M500 Multi-cell: Configure this setting for a specific base station. This is NOT a site-wide setting.

Important Note for M500 only: 

Starting with firmware version 1.14.4, we've simplified the firmware upgrade process by providing the M500 unified firmware image (M500-x.x.x-unified.img), which includes the firmware for the base station, handset, and cordless deskset in one file. This is the only file required to update all devices within the M500 family of products.

To utilize the unified firmware image, configure provisioning.firmware_url to point to the unified image. Ensure that provisioning.handset_firmware_url and provisioning.cordless_deskset_firmware_url are set to null using the following configuration:

provisioning.handset_firmware_url = %NULL
provisioning.cordless_deskset_firmware_url = %NULL

Alternatively, though not recommended, if there is a need to use a different firmware version for the handset or deskset, you can update provisioning.firmware_url , provisioning.handset_firmware_url and provisioning.cordless_deskset_firmware_url with different versions of the individual firmware images (M500-x.x.x.img, M55-x.x.x.img, and M58-x.x.x.img, respectively).