Write a script for the Asterisk open source PBX, complete with detailed installation instructions, that does the following:
1) Internal user dials a special feature code (for example, *66).
2) User is prompted to enter the phone number.
3) It dials the phone number.
4) If the phone number is busy, it hangs up, waits 3 seconds, then goes back to 3)
5) If the line is ringing, it lets the call go through.