Hi,
If you are talking about analog devices connected to FXS ports in the voice gateway, you can define DNs and control those devices with the CM via MGCP.
If you don't want MGCP, you can define DNs and control analog devices with H.323 in the voice gateway.
In this case you define the DNs with dial peer configurations.
Reference links:
Dial Peer Configuration on Voice Gateway Routers:
http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/dial_peer/dpeer_c.html
Info about MGCP:
http://www.cisco.com/en/US/tech/tk652/tk701/tk419/tsd_technology_support_sub-protocol_home.html
Info about H.323:
http://www.cisco.com/en/US/tech/tk652/tk701/tk309/tsd_technology_support_sub-protocol_home.html
Hope it helps, if it does please rate.
Best regards.