Arrangement having a first module and a redundant, second module, which monitor one another mutually, for which purpose: - each of the two modules (21, 22) contains a current source or voltage source (27, 39), which either is designed to be capable of being switched on and off and is connected via a first current sensor (29, 38) to a first line terminal (30, 40) of the module concerned, or is connected to the first line terminal (30, 40) via a series circuit composed of a first controllable switch (28, 37) and the first current sensor (29, 38); - each of the two modules (21, 22) also has a second line terminal (33, 43) and a ground terminal, between which lies a second current sensor (31, 41) in series with a second controllable switch (32, 42); - the first line terminal of the first module is connected via a first line to the second line terminal of the second module, and the first line terminal of the second module is connected via a second line to the second line terminal of the first module; - each of the two modules (21, 22) is designed, when in the functioning state, to switch on its current source or voltage source (27, 39) and to close the second controllable switch (32, 42) contained in said module or to close both of the controllable switches (28, 32, 37, 42) contained in said module; and - each of the two modules (21, 22) contains a monitoring device (35, 45) connected to the two current sensors contained (29, 31, 38, 41) in said module, which monitoring device generates a monitoring signal (36, 46) identifying the corresponding other module as functioning if at least one of the two current sensors (29, 31, 38, 41) detects a current flow. - each of the two modules (21, 22) contains a current source or voltage source (27, 39), which either is designed to be capable of being switched on and off and is connected via a first current sensor (29, 38) to a first line terminal (30, 40) of the module concerned, or is connected to the first line terminal (30, 40) via a series circuit composed of a first controllable switch (28, 37) and the first current sensor (29, 38); - each of the two modules (21, 22) also has a second line terminal (33, 43) and a ground terminal, between which lies a second current sensor (31, 41) in series with a second controllable switch (32, 42); - the first line terminal of the first module is connected via a first line to the second line terminal of the second module, and the first line terminal of the second module is connected via a second line to the second line terminal of the first module; - each of the two modules (21, 22) is designed, when in the functioning state, to switch on its current source or voltage source (27, 39) and to close the second controllable switch (32, 42) contained in said module or to close both of the controllable switches (28, 32, 37, 42) contained in said module; and - each of the two modules (21, 22) contains a monitoring device (35, 45) connected to the two current sensors contained (29, 31, 38, 41) in said module, which monitoring device generates a monitoring signal (36, 46) identifying the corresponding other module as functioning if at least one of the two current sensors (29, 31, 38, 41) detects a current flow.