How to use the asterisk as a local phone

Recently,I have joined a project,there are some trouble faced,please help me,thanks very much!!!
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* when i learn asterisk,in the /etc/asterisk/extensions.conf,we can write a dialplan,at the time i call someone,i can hear the sound play by the fucttion in the extensions.conf called playback(filename) or background(filename).
And now i don’t want to do as this,if i was the asterisk server ,when some one called me,i don’t want to playback() some sound or turn the call to other people,i just want to talk to who called directly with the local sound card.that means that how can i use the asterisk as a local phone!

For Linux, there are two soundcard channel drivers. However, compared with a proper soft phone, on the same machine, they are rather limited.