Activate (validate) the ticket
The first time you travel with a new ticket you must activate (validate) your ticket by having a validator scan the travelcard. Validation may be compared to stamping a paper ticket. When you get on a bus up front, you must always have your travelcard scanned. This is the driver's way of controlling your ticket. This applies to all green regional buses and the red "single buses".
Read more about using the travelcard.