A measuring device having a detector with at least one detector element and, connected downstream of the detector, a DC voltage amplifier with at least one input (and at least one output. In the holder, a cable-insertion hole into which the flat cable is inserted is provided. If the detected signal quality is at or below a first threshold and decreasing over a first detection time interval, then the mobile wireless communication device estimates a maximum response time interval until the detected signal quality of the radio frequency link is below a second threshold. 2 percent by mass in terms of phosphorus, an amide compound in an amount of 0. The central database server can collect and store data from CPAP apparatus for a number of patients who undergo sleep therapy. Focusing in this manner may prevent or reduce stimulation of adjacent non-target brain regions.