This one is for direct dialing of 17162896926

Dial-peer voice 9999 pots

destination-pattern 17162896926

This one is for dialing out to your PRI using the outbound access code of 8.

dial-peer voice 10 pots

preference 1

destination-pattern 8T

This is for 911 dialing.

both dial-peers 8911 and 911 are for dialing 911

Dial peers 100, 101 and 200 are for 4 digit dialing across the WAN to your pub and sub more than likely.

dial-peer 300 and 301 are shut down but is used to send extension 3155/2975 across the wan to either a ccm or another gateway.

Dial-peer 2975 will send numbers to 17166262617 across the pri.

the rest of the dial-peers with port 0/2/0, 0/2/1, and 0/2/2 are used to send four digits out those mandated ports. Those can either be FXO or FXS ports.

good info for dial-peer configuration and understanding!

http://www.cisco.com/en/US/docs/ios/12_2/voice/configuration/guide/vvfpeers.html#wp1241411