I talked to a phone tech recently and while he already knew about this method he said it won't work on Protel phones because the dtmf control system is separate from the payments received system. Apparently Protel phones have a secret button which, when pushed and held down, allows anybody to manually open the lock on the money box and slide the money box out of the phone. The downside is that it doesn't open the moneybox. This was done because Protel's contract to use Abloy locks expired one year and Abloy was threatening to sue them for the use of the locks in existing payphones and threatened to get a court order to confiscate the keys. As a backup plan in case Abloy ever went through with the threat the secret button was installed in all newer Protel phones.
