time between recharging is one design concern addressed by power interface 504 i power interface 500 i is configured to perform power management functions for the system as well as monitor the status of main power 504 and report such status to devices electrically associated with buss 502 such as processing device 500 power interface 504 i dynamically addresses power management issues by selectively powering down unutilized devices for the preferred embodiment power interface 504 i is a cpld that generates chip select signals and powers down the various assps as desired alternatively processing device 500 may perform such power management functions electronic lock 540 is electrically associated with processing device 500 through lock interface 540 i and buss 502 for this embodiment lock interface 540 i is an assp or cpld device configured to change the state of electronic lock 540 in response to control signals received from processing device 500 similarly lock interface 540 i may be further configured to communicate the status of electronic lock 540 to devices electrically associated with buss 502 electronic lock 540 may be a software lock that prevents access to various functions provided by user interface 500 in addition electronic lock 540 may further be a mechanical lock that prevents they hydrant.