System and portable device for transmitting identification signals

A portable device for transmitting signals to a second device to transmit data from the portable device to the second device, wherein the portable device is wearable by a user, the device comprising:

• at least two electrodes and
• an output driver for applying an electrical signal between the electrodes such that the signal is able to be coupled into the body of the user by the electrodes and detected by at least one electrode of the second device,
• wherein the portable device is capable of transmitting identification information,
• wherein the mentioned output driver for applying the electrical signal between the electrodes is a part of transmitter electronics, which transmitter electronics is capable of generating the electrical signal dependent upon specified data, and wherein the transmitter electronics are implemented as an application-specific integrated circuit (ASIC), the application specific integrated circuit comprising:
• a modulator for generating an electrical signal dependent upon specified data and
• the output driver for applying the electrical signal between the electrodes,
• the application-specific integrated circuit being designed for the end of communicating to the second device a signal concerning a battery charge level of a feed of the integrated circuit.