a plural - frequency capacitive occupancy sensing system comprises an antenna electrode and a detection circuit , which is configured to drive the antenna electrode at least with a first and a second signal at a first and a second frequency , respectively , so as to obtain at least a first and a second measurement value indicative of at least one of conductance , susceptance , resistance , reactance and capacitance between the antenna electrode and a reference node , at the first frequency and the second frequency , respectively . the detection circuit compares the capacitance between the antenna electrode and the reference node with a threshold capacitance , the threshold capacitance being derived from a difference between the first and second measurement values and / or the capacitance between the antenna electrode and the reference node being corrected based upon the difference between the measurement values . the detection circuit outputs an occupancy state signal depending on the comparison .