Power supply interface

A power supply adapter for a mobile telephone unit having an operating voltage range between a maximum and a minimum operating voltage, said power supply adapter comprising:

• a cable having two ends, one end being connected to an external voltage source supplying power to the mobile telephone unit, the terminal voltage of said external voltage source being higher than the maximum operating voltage, and the other end being connected to a voltage regulator unit delivering a controlled output voltage within the permitted operating voltage range, said voltage regulator unit being provided in a housing adapted to be connected to the mobile telephone unit, wherein said cable is a resistive cable the resistance and length thereof being such that when the mobile telephone is subjected to a maximum load over extended periods a major part of the power losses arising from the voltage to be dropped by the cable and the voltage regulator will be absorbed by the resistive cable and the remaining power losses are absorbed by the voltage regulator.