Can not call between extensions

I just installed new FreePBX 2.6.0RC2 on top Asterisk 1.6.2. My system has a 12 port card with 5 FXS ports. I created 5 extensions one per channel on those FXS ports.

When analog phone is off hook, I can hear dial tone. But anything I pressed on the phone will give me busy tone.

Thanks for any help you may provide.