FIELD: power supplies for portable telephone sets. SUBSTANCE: portable telephone set has internal storage battery; external portable battery power supply is secured to telephone set for removal. Control device incorporated in telephone set functions to control connection of respective batteries to power input of telephone set depending on detection of external battery voltage. All time when external battery voltage is higher than predetermined minimal value, it will be connected to power input of telephone set to ensure power supply to the latter thereby extending service life of internal battery. When external battery voltage drops below minimal value or this battery is removed, device automatically switches telephone set over to internal battery supply and therefore external battery may be replaced without interrupting power supply to telephone set when the latter is turned on or call is set up. EFFECT: enhanced stability of power supply. 2 cl, 3 dwg, 3 tbl
