Abstract: An electronic device supplied power from either a single rechargeable battery or four non-rechargeable batteries. The single rechargeable battery is preferably a 4.8 volt, DURACELL DR-121 rechargeable battery which includes a first end having positive and negative terminal contacts, a pair of recharging contacts and a key. Each of the four non-rechargeable batteries are preferably AA size, lithium batteries and are configured so that a first pair of batteries in series are in parallel with a second pair of batteries in series. The electronic device comprises a housing shaped to include a battery cavity which can accept either type of battery source. The battery cavity comprises a bottom wall, a front end wall, a back end wall and a pair of sidewalls. One of the sidewalls includes a slot which is sized and shaped to accept the key of the rechargeable battery, the slot enabling the rechargeable battery to be inserted in the battery cavity only in its proper orientation relative to the battery cavity.