After calling someone and hearing a busy signal, hang up.
L ift up handset and listen for dial tone.
You will hear a confirmation tone that indicates the busy line will be monitored for the next 30 minutes. When the line is free, your phone will ring two quick rings. Pick up the phone and it will automatically call the number you are trying to reach. Lift the handset and listen for the dial tone. You will automatically be connected to the last number that called you.