Is there a delay between 'debits'? - or does it rely on touching in and touching out?
What about contactless debit cards? Can one card be used for several people travelling together?
If you send the Visitor Oyster Card to the address below, you can get a refund of any remaining credit:
TfL Customer Services, 14 Pier Walk, 4th Floor, London, SE10 0ES.
Please remember to include a covering letter explaining why you are returning the card. You will then be sent a cheque in GBP.
The Oyster card platform is due to be replaced by a contactless payment card system by June 2015.