How to factory reset Cisco ATA 186 ?
* Power up the ATA
* Make sure the ATA is *NOT* plugged into the network.
* Plug an analogue phone into voice port one.
* Lift the handset, and press the button on top of the ATA
* You will be greeted by the American female darlek.
* Dial 322873738#*
Thanks Abhishek Sharma It worked for me.