control logic for instance in the form of hardware gates alternatively the controller 11 may be for example programmable hardware with embedded firmware for instance the controller 11 may comprise a microprocessor arrangement as shown in fig1 here the controller 11 comprises a processor 30 that is connected to a memory 31 and to input outputs 32 the memory is provided with one or more computer programs 33 the one or more programs 33 include instructions that when executed by the process control it to perform a method of controlling the switch 23 and thus controlling operation of the device 10 based on decisions made using information received from the voltage detecting module 22 and the sim 19 this is explained in more detail below particularly with reference to fig2 the computer program instructions 33 may arrive at the controller 11 via an electromagnetic carrier signal or be copied from a physical entity such as a computer program product or memory device 34 or a record medium such as a cd rom or dvd 35 fig2 is a flowchart illustrating operation of the device particularly the controller 11 the operation of fig2 starts at step s 1 when the device 10 is powered up at step s 2 the type of the sim 19 is detected this is achieved by the controller 11 sending a request for.