External Call dial Extension

Hi i have installed FreePBX 13.0.1.
I have 4 fxo Lines
When i recive a call, the PBX have a Ring Group whit some Extensions, and play a Announcement.

i Like to know how, the people call to my PBX if know the extension number can dial and ring only this extension number.

When i call to my PBX i dial any Extension on the Announcement, and no take any effect, ring all extension on the Ring Group.


Sorry my english