Abstract: An intrinsically safe field device of automation technology comprises connection terminals via which a current can be supplied; a sensor element and/or actuator element; field device electronics with a current path between the connection terminals and a voltage regulator incorporated into the current path; and an explosion protection unit comprising at least two controllable switching elements, incorporated into the current path in series, and two threshold value circuits designed such that a first threshold value circuit controls a first switching element as a function of a first threshold value, and a second threshold value circuit controls a second switching element as a function of a second threshold value, such that, upon the first and/or second threshold value being reached, the current is limited to the first and/or second threshold value, and the threshold value circuits are connected in parallel to the voltage regulator.

Abstract: A method for operating an automation field device comprises connecting a two-conductor line with an input terminal of the field device; setting a minimum electrical current value at the input terminal of the field device in an initializing phase; measuring a maximum voltage value at the input terminal in the initializing phase; ascertaining a minimum supplemental power supplied to the field device at the input terminal and which is available to the field device for performing at least one supplemental functionality; and activating/switching on a supplemental module by the processing unit when the ascertained minimum supplemental power is greater than or equal to an operating power needed for operating the supplemental module, wherein by the activating/switching on of the supplemental module a corresponding supplemental functionality is performed by the field device in measurement operation.