Things that drain batteries faster: o Pressing keys! Of course, you don't get much out of your HP48 if you don't press a key now and then, but holding keys down more than minimally necessary is a great battery drainer. In particular, the technique of holding down the Alpha key while typing text drains batteries more than locking the Alpha shift. If you commonly type three or more consecutive alpha characters, you may save keystrokes by doing -60 SF, which thereafter causes a single press of the Alpha key to lock alpha shift on, instead of the default two consecutive presses. If you are typing mostly lower-case, pressing left-shift alpha while already in alpha entry mode thereafter produces lower-case text by default and capitals only after left-shift, which is just the reverse of the initial alpha entry mode (this lasts only during the current editing session or until left-shift alpha is repeated). o Leaving the serial port on after data transfer. Any data transfer turns the serial port on, but nothing turns it off again except either a CLOSEIO command or turning the calculator OFF. It might therefore prolong battery life to make it a habit to turn the HP48 OFF after any manually-initiated data transfer, or to include a CLOSEIO command as part of every program which uses the serial port (and don't forget to use IFERR data-transfer THEN ... END CLOSEIO so that the serial port will get turned off even after an error or Cancel key). The SERVER mode also turns on the serial port. o Beeping. If you can notice error messages even without the audible reminder, you could turn the Standard Beep off (-56 SF). Your neighbors in study hall or who are taking the same test may also thank you. Perhaps an ordinary alarm clock is almost as good as an HP48 to wake you up each morning! o Displaying the ticking clock for extended periods. The ticking clock does a complete date calculation and display routine once every second while this feature is on; that's 3600 times per hour, or several extra minutes of program-running time per hour. Of course, the ticking clock is only updated while it is visible and no program is running. o Displaying the blinking cursor for extended periods. I have no specific data, but it certainly takes a bit of activity to change the cursor every 1/2 second. o Leaving the calculator on. Sure, it will shut itself off after 10 minutes, and it will only use about 50% as much power as when running a program, but this means that 10 minutes of "light sleep" is about as much drain as 5 minutes of running a program. If you know you are through using it for some while, then it might pay to turn it off yourself. o Zapping the zener diodes. That idea to reverse the batteries momentarily to reset a hang was evidently not so great; it may have turned the protective zener diodes into smokey resistors which may forever afterwards place a drain on the batteries. Be kind to your HP48 and always insert new batteries facing the right way. Can an overwhelming electrostatic blast ever cause a similar effect? How about those internal modifications made in the electronics shop? o Playing Doom with too many enemies... overload...overLoad...oVerLoad...OVeRLoAD...OVerLOAD...OVeRLOAD...OVERLOAD!! ----------------------------------------------------------- With best wishes from: John H Meyers ( jhmeyers@mum.edu )