An electrotransport drug delivery device comprising an electrical module and a reservoir module, the electrical module and the reservoir module being configured to be combined to form a unitary, activated drug delivery device prior to use, wherein: the electrical module comprises: circuitry; an electrical output adapted to connect the circuitry to an electrical input on the reservoir module when the electrical module is combined with the reservoir module; at least two power-on contacts (272, 274) between the circuitry and a battery; and the battery, which is adapted to be isolated from the circuitry by the power-on contacts while the power-on contacts remain open, and which is adapted to be connected into the circuitry when the power-on contacts are closed by battery contact actuators on the reservoir module when the electrical module and the reservoir module are combined; and the reservoir module comprises: the electrical input adapted to electrically connect the circuitry in the electrical module to at least a pair of active electrodes in the reservoir module when the electrical module is combined with the reservoir module; and the battery contact actuators each configured to close a corresponding power-on contact when the electrical module is combined with the drug reservoir, such that the battery is connected into the circuitry and the device is powered on; characterized in that the device is configured to increment a logic flag when the electrical module is combined with the reservoir module, and wherein the device is configured such that, if the logic flag has met or exceeded a predetermined value, the device will either not power on or will power off if it has already powered on. the electrical module comprises: circuitry; an electrical output adapted to connect the circuitry to an electrical input on the reservoir module when the electrical module is combined with the reservoir module; at least two power-on contacts (272, 274) between the circuitry and a battery; and the battery, which is adapted to be isolated from the circuitry by the power-on contacts while the power-on contacts remain open, and which is adapted to be connected into the circuitry when the power-on contacts are closed by battery contact actuators on the reservoir module when the electrical module and the reservoir module are combined; and circuitry; an electrical output adapted to connect the circuitry to an electrical input on the reservoir module when the electrical module is combined with the reservoir module; at least two power-on contacts (272, 274) between the circuitry and a battery; and the battery, which is adapted to be isolated from the circuitry by the power-on contacts while the power-on contacts remain open, and which is adapted to be connected into the circuitry when the power-on contacts are closed by battery contact actuators on the reservoir module when the electrical module and the reservoir module are combined; and the reservoir module comprises: the electrical input adapted to electrically connect the circuitry in the electrical module to at least a pair of active electrodes in the reservoir module when the electrical module is combined with the reservoir module; and the battery contact actuators each configured to close a corresponding power-on contact when the electrical module is combined with the drug reservoir, such that the battery is connected into the circuitry and the device is powered on; the electrical input adapted to electrically connect the circuitry in the electrical module to at least a pair of active electrodes in the reservoir module when the electrical module is combined with the reservoir module; and the battery contact actuators each configured to close a corresponding power-on contact when the electrical module is combined with the drug reservoir, such that the battery is connected into the circuitry and the device is powered on;