Cisco ATA186-I1 Installation And Configuration Manual page 73

Chapter 6 Upgrading the Cisco ATA 186 Software
About the Software Upgrade Process
To help you identify the correct files to place on your TFTP server, the
Note
TFTP-method file containing the Cisco ATA 186 software has a ".kxz"
extension.
Cisco ATA 186 Installation and Configuration Guide
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