An electronic power supply circuit for battery-powered hardware devices is disclosed which can be electronically switched to supply any of at least two predetermined voltages wherein the batteries are switched in parallel or in series depending on the desired voltage. Also disclosed is an electronic apparatus comprising the electronic power supply circuit, which in some modes of operation uses the highest of the two predetermined voltages and which in other modes of operation can function with the lower of two predetermined voltages, and includes control logic that switches the electronic power supply circuit to supply said higher voltage when the apparatus in a mode in which it uses this higher voltage and that switches said electronic power supply circuit to supply said lower voltage at least during some of the modes in which the apparatus can function with the lower voltage.