Kumar, go to http://www.cisco.com and make a search for ata 186. It will show you web pages with technical info and configuration howto for ata. Basically you can configure the ATA via phone.
Moya, the answer is yes. You can use the ATA from Vonage as a phone line connected to the Quintum PSTN. I’ve tried this once. The problems I had were related with IVR. When somebody calls the ATA number cannot hear the voice prompts from Quintum. If anybody find a workaround, please let me know.