a modular automated external defibrillator system includes a base unit and at least one interconnected module . the base unit typically includes a functional circuit and includes an interface that couples the functional circuit to the module . likewise , the module includes an interface that couples the module to the base unit . by manufacturing such modular aed models instead of one - piece , i . e ., integrated , aed models , a manufacturer can reduce the cost and complexity of its manufacturing process . furthermore , the manufacturer may be able to bring such a modular aed to market more quickly than it could bring an integrated model of the aed to market . moreover , a modular aed allows the manufacturer and customer flexibility in respectively providing and selecting feature sets . in addition , a customer can obtain replacements for broken modules , and the manufacturer can provide cheaper upgrades by upgrading a module or base unit instead of upgrading the entire aed .