A neuro stimulation system comprising: an implantable neural stimulator unit, for stimulation of target neural tissue, with a coil; and an external unit comprising: a coil inductively coupleable to the coil of the implantable neural stimulator unit when in close proximity to each other, an RF-signal generating module for generating and outputting an RF-signal to the coil of the external unit for inductive power and/or data transfer to the implantable neural stimulator unit, a measurement unit connected to the coil of the external unit for measurement of an electrical parameter at the coil of the external unit, and a controller connected to the measurement unit and comprising a comparator and a storage for storing the electrical parameter, wherein the controller is configured to operate at least in normal operating and corrective action mode, and when in the normal operating mode to repeatedly: i. measure the electrical parameter with the measurement unit; ii. determine, with the comparator, a change of the measured electrical parameter in relation to the stored electrical parameter; iii. switch the controller into the corrective action mode when the change exceeds a threshold; and otherwise iv. modify the stored electrical parameter by the measured electrical parameter; and v. determine a new value for the threshold, as a function of the stored electrical parameter, such that the new value accounts for a change in distance between the external unit and the implantable neural stimulator unit; and when in corrective action mode, to put at least part of the external unit into a low power mode only after failure to obtain, in response to a sent command, a reply from the implantable neural stimulator unit. an implantable neural stimulator unit, for stimulation of target neural tissue, with a coil; and an external unit comprising: a coil inductively coupleable to the coil of the implantable neural stimulator unit when in close proximity to each other, an RF-signal generating module for generating and outputting an RF-signal to the coil of the external unit for inductive power and/or data transfer to the implantable neural stimulator unit, a measurement unit connected to the coil of the external unit for measurement of an electrical parameter at the coil of the external unit, and a controller connected to the measurement unit and comprising a comparator and a storage for storing the electrical parameter, a coil inductively coupleable to the coil of the implantable neural stimulator unit when in close proximity to each other, an RF-signal generating module for generating and outputting an RF-signal to the coil of the external unit for inductive power and/or data transfer to the implantable neural stimulator unit, a measurement unit connected to the coil of the external unit for measurement of an electrical parameter at the coil of the external unit, and a controller connected to the measurement unit and comprising a comparator and a storage for storing the electrical parameter, wherein the controller is configured to operate at least in normal operating and corrective action mode, and when in the normal operating mode to repeatedly: i. measure the electrical parameter with the measurement unit; ii. determine, with the comparator, a change of the measured electrical parameter in relation to the stored electrical parameter; iii. switch the controller into the corrective action mode when the change exceeds a threshold; and otherwise iv. modify the stored electrical parameter by the measured electrical parameter; and v. determine a new value for the threshold, as a function of the stored electrical parameter, such that the new value accounts for a change in distance between the external unit and the implantable neural stimulator unit; and when in corrective action mode, to put at least part of the external unit into a low power mode only after failure to obtain, in response to a sent command, a reply from the implantable neural stimulator unit. i. measure the electrical parameter with the measurement unit; ii. determine, with the comparator, a change of the measured electrical parameter in relation to the stored electrical parameter; iii. switch the controller into the corrective action mode when the change exceeds a threshold; and otherwise iv. modify the stored electrical parameter by the measured electrical parameter; and v. determine a new value for the threshold, as a function of the stored electrical parameter, such that the new value accounts for a change in distance between the external unit and the implantable neural stimulator unit;