This has been asked and answered several times on this board. Reference this board or cisco.com for "auto ring down". But because I'm in a good mood this morning, here is a brief explanation. You basically create a calling search space that contains a single partition. In that single partition, you assign a translation pattern. The translation pattern translates 'blank' to whatever number you want the phone to call. Then, assign the special calling search space to the calling phone. When the person picks up the handset or hits speakerphone, the translation pattern will match 'blank' and automatically call the extension you specified.
John Lever
Telecommunications
Richland School District Two