The invention relates to a device (1) and a corresponding method for monitoring a two-wire line (2), in particular a two-wire line (2) of a fire protection system. The device (1) comprises a passive terminating component (10) for terminating the two-wire line (2), wherein the passive terminating component has a chargeable energy storage (12), a constant current source (20) for providing a measuring current (I1) to the passive terminating component, a voltage detection unit (30) for detecting a voltage curve (V1) at output terminals (4, 6) of the two-wire line (2), a control unit (40) for controlling the constant current source (12) and for evaluating the detected voltage curve, the control unit (40) being configured to separately determine a series resistance (RL) and a parallel resistance (PS) of the two-wire line (2).