In a method for operating an electronic battery-powered hearing instrument, the following steps are performed: providing primary function means with power from the battery via a first power supply terminal and a second power supply terminal, and via a rectifier circuit for providing a positive supply voltage and a negative supply voltage regardless of the polarity of the battery relative to the first and second power supply terminal, inferring the status of an input means, wherein a first terminal of the input means is electrically connected to the first power supply terminal, and a second terminal, of the input means is electrically connected to an input line, from an input voltage, that is, a voltage of the input line. A programming device for a hearing instrument according to the invention and a method for operating a programming device are adapted to the possibility of the hearing aid having an inverted power supply. They are configured to detect the polarity of the battery or other power supply, or, correspondingly, the status of the hearing aid's rectifier.