Abstract: A paging radio receiver system includes a paging radio receiver having an EEPROM storing a predetermined specific pass word, and an access unit comprising an input apparatus, and a comparator comparing a pass word supplied from the input apparatus with the specific pass word, and an access circuit for access to the EEPROM. The comparator supplies an access enabling signal to the access circuit when the supplied pass word is equal to the predetermined specific pass word.

Abstract: A battery pack mounting device for portable radio equipment having a built-in antenna. The device determines a position of a battery pack, which powers the equipment, inserted in a battery pack accommodating portion provided in the equipment. Various constants which determine the antenna characteristic of the equipment are controlled on the basis of the determined position of the battery pack, thereby maintaining the optimum antenna characteristic at all times. When the device is applied to a charging unit which charges a rechargeable battery, the opposite electrodes of the battery are electrically correctly connected to a pair of connecting terminals which are provided in the charging unit and connected to opposite poles of a charging circuit as the battery pack is inserted in a battery chamber defined in the charging unit. Even when the battery pack is placed in the battery chamber upside down, the opposite electrodes of the battery are accurately connected to the connecting terminals of the charging unit.