A system is provided with a portable device (31) for the transmission of signals to a second device, wherein the portable device (31) is wearable on the body of a user. The portable device (31) includes at least two electrodes (3, 4) and transmitter electronics (7) for applying an electrical signal between the electrodes, in such a way that the signal between the electrodes (3, 4) is able to be coupled into the body of the user and detected by at least one electrode of the second device. The transmitter electronics are an application specific integrated circuit and thus include both means for the production of electrical signals that are dependent upon specified data, as well as means for applying the electrical signal between the electrodes. The means for generating electrical signals that are dependent upon specified data are typically digital circuits for the encoding of specified data that are to be transmitted and for the modulation of the data that are so encoded.