Precondition: You have dialed an internal number and hear a busy signal. It is important that you reach the called party. 

Press the key. LED flashes. Enter the code. 

The called party and person to whom this party is talking hear an alerting tone every two seconds.
If the called party has a system telephone with display, the following appears on the screen: "Override: (station no. or name)". 

You can now start talking.