A data transfer apparatus for use in association with a field generator of a TTFields (tumor-treating fields) therapy system, the field generator having a first connector that is used to output AC signals and convey serial data, the data transfer apparatus comprising: a serial data transceiver; a memory; a modem (70, 72); and a second connector configured to interface with the first connector of the field generator; characterized by: a controller programmed to execute instructions that cause the data transfer apparatus to execute the following steps: determining if the field generator has been connected to the data transfer apparatus; after determining that the field generator has been connected to the data transfer apparatus, causing the serial data transceiver to accept serial data from the field generator and store the accepted data in the memory, wherein the accepted data is data relating to treatment of a patient using TTFields; after accepting the data from the field generator, determining whether the field generator has been disconnected from the data transfer apparatus; and after determining that the field generator has been disconnected from the data transfer apparatus, retrieving data relating to treatment of a patient using TTFields from the memory and causing the modem (70, 72) to transmit the retrieved data to a remote server. a serial data transceiver; a memory; a modem (70, 72); and a second connector configured to interface with the first connector of the field generator; characterized by: a controller programmed to execute instructions that cause the data transfer apparatus to execute the following steps: determining if the field generator has been connected to the data transfer apparatus; after determining that the field generator has been connected to the data transfer apparatus, causing the serial data transceiver to accept serial data from the field generator and store the accepted data in the memory, wherein the accepted data is data relating to treatment of a patient using TTFields; after accepting the data from the field generator, determining whether the field generator has been disconnected from the data transfer apparatus; and after determining that the field generator has been disconnected from the data transfer apparatus, retrieving data relating to treatment of a patient using TTFields from the memory and causing the modem (70, 72) to transmit the retrieved data to a remote server. determining if the field generator has been connected to the data transfer apparatus; after determining that the field generator has been connected to the data transfer apparatus, causing the serial data transceiver to accept serial data from the field generator and store the accepted data in the memory, wherein the accepted data is data relating to treatment of a patient using TTFields; after accepting the data from the field generator, determining whether the field generator has been disconnected from the data transfer apparatus; and after determining that the field generator has been disconnected from the data transfer apparatus, retrieving data relating to treatment of a patient using TTFields from the memory and causing the modem (70, 72) to transmit the retrieved data to a remote server.