The smartcard contains a memory chip on which data is stored. The metallic contacts allow a smartcard reader to connect directly to the memory chip for reading or writing data. Data capable PAP machines have a built in reader for writing breathing data to the smartcard. Respironics and Resmed use smartcards to transfer data from PAP machines to computers. Puritan Bennett uses a data cable that connects directly from the xPAP machine to the computer. Another difficulty that can arise is that the card gets bent or warped too much and broken inside. Best bet is to always have a spare card on hand.