comprises among other things the detection of the battery state 74 and preferably the following inputs pwr_bt and bt_pre for the turning on and turning off of various stages of a power saving operation lcm_bt for the activation of the sending out of signals over the electrodes 3 4 for example during a specified time if the transmitter electronics 7 themselves are in u201c low comfort mode u201d mot_det 1 2 for at least one movement detector or activity detector 44 and wu_ext for an external in particular wirelessly received wake up signal u201c wake up u201d for example by a 125 khz receiver thereby it can be achieved that the transmitter electronics 7 are only activated when in the proximity of a receiver for this purpose the receiver which for example is stationary or built into an automobile is equipped with a corresponding 125 khz sender for the sending out of a wake up signal output signals led 1 led 2 control leds for notification of the battery status output signals eol_hi eol_lo further denote the battery level and can be for example by the portable device 31 queried and processed finally in fig8 a further possible embodiment of an u201c end of battery life u201d characteristic is.