Test device for checking polarities of poles (9 to 12) of DC voltage sources (13, 14), which poles are individually connected to inputs (4 to 7) of a combination circuit, which inputs are not connected to one another, with respect to a reference-ground potential, the test device comprising - at least two electrical contacts (2, 3, 51, 52) respectively associated with one of the inputs (4 to 7) and connectable thereto and - a signal element, wherein - the at least two electrical contacts (2, 3, 51, 52) are associated with inputs (4, 5), which are respectively provided for one of the poles (9 to 12) of one of at least two of the DC voltage sources (13, 14), and - each of the at least two electrical contacts (2, 3, 51, 52) is connected to a respective switching element (23, 24, 59, 60), which blocks an electrical signal to the signal element depending on the polarity of a voltage applied to the electrical contact (2, 3, 51, 52) with respect to the reference-ground potential, characterized in that - the switching elements (23, 24, 59, 60) are electrically connected in series and - each of the switching elements (23, 24, 59, 60) is configured to block the electrical signal to the signal element in the event that the polarity of the voltage applied to the electrical contact (2, 3, 51, 52) does not match a polarity prescribed for the respective electrical contact (2, 3, 51, 52) with respect to the reference-ground potential, - such that the signal element is supplied with the electrical signal for outputting a match signal only in the event that all of the polarities of the voltages applied to the at least two electrical contacts (2, 3, 51, 52) via the associated inputs (4 to 7) match the respectively prescribed polarities with respect to the reference-ground potential. - at least two electrical contacts (2, 3, 51, 52) respectively associated with one of the inputs (4 to 7) and connectable thereto and - a signal element, - the at least two electrical contacts (2, 3, 51, 52) are associated with inputs (4, 5), which are respectively provided for one of the poles (9 to 12) of one of at least two of the DC voltage sources (13, 14), and - each of the at least two electrical contacts (2, 3, 51, 52) is connected to a respective switching element (23, 24, 59, 60), which blocks an electrical signal to the signal element depending on the polarity of a voltage applied to the electrical contact (2, 3, 51, 52) with respect to the reference-ground potential, - the switching elements (23, 24, 59, 60) are electrically connected in series and - each of the switching elements (23, 24, 59, 60) is configured to block the electrical signal to the signal element in the event that the polarity of the voltage applied to the electrical contact (2, 3, 51, 52) does not match a polarity prescribed for the respective electrical contact (2, 3, 51, 52) with respect to the reference-ground potential, - such that the signal element is supplied with the electrical signal for outputting a match signal only in the event that all of the polarities of the voltages applied to the at least two electrical contacts (2, 3, 51, 52) via the associated inputs (4 to 7) match the respectively prescribed polarities with respect to the reference-ground potential.