You can upgrade an ATA186 remotely by using TFTP. The TFTP method of configuration is useful when you have many Cisco ATA because you can use aTFTP server for remote, batch configuration of Cisco ATAs.
You need to provision the ATA186 to use TFTP (UseTftp)and provide a TftpURL.You might need to create a profile for the ATA186 that you want to upgrade. The CFGFMTformatting tool is used to convert the profile from TEXT to BINARY.
At the specified interval (CfgInterval), the ATA186 will download the updated profile from the designated TftpURL. If you want force the ATA 186 to check immediately, open a browser and enter the URL /refresh
You can find a detailed procedure here:
http://www.cisco.com/univercd/cc/td/doc/product/voice/ata/ataadmn/sccp3_0/sccpag.pdf