Abstract: An arrangement has a tachograph, an external mobile data memory device with an external second interface, the interface corresponding with the first interface, for providing data transmission. For safety reasons, conventional arrangements provide for a complete mechanical isolation of the memory device during transmission, the memory device being configured as a data card. In order to reduce cost without compromising safety, the tachograph has a first encoding unit associated to an interface of the tachograph and the data memory device has a second encoding unit to enable data transmission in encoded form.