A method for activating functions of at least one tachograph having a control unit and an interface. The control unit is activated by a program to perform a first group of functions. First, a connection of an external storage medium to the interface of the at least one tachograph is established. The storage medium has at least one instruction for activating a function, which can be read out by the control unit. An authentication between the external storage medium and the control unit also takes place. The function associated with the at least one instruction is activated in such a way that the function is associated with the first group of the control unit. Next, the connection between the external storage medium and the interface of the at least one tachograph is released.