Abstract: In apparatus powered by electric batteries (e.g.: a paging receiver) having a battery compartment including means to couple the battery in it with a battery charger, the negative (-) charging contact is located at a position nearer to one end of the battery compartment than to the opposite end. A rechargeable battery (e.g.: Ni Cad) has a band of its insulated cover removed at a corresponding position so that the negative charging contact can touch the underlying portion of the battery container, and through that connection the charging circuit can be closed. The charging circuit cannot be closed if the battery is inserted with its polarity reversed. When a non-rechargeable battery is installed the recharging-circuit contact mates with a part of the insulation cover of the battery and the charging circuit cannot be closed. In one disclosed embodiment of the invention, if either battery is installed with its polarity reversed, the energizing circuit from the battery to the radio apparatus will not close.