Regarding cisco ata 186 (h323 ) with asterisk

i have a cisco ata 186 that has h323 firmware…

i want to connect pots phone to ata 186 and to register with asterisk server and to make calls only internally…

since the firmware that cisco ata uses is H323 i dont know how to configure asterisk server to make call internally… please give me details to configure asterisk…

I suppose it will be much easier to find the SIP firmware for that ATA and upgrade it.