whether the counter state is already equal to n if the counter state is equal to n in step 36 then the stored counter value i e the counter state value at which the tooth is broken is sent to the control in step 44 and subsequently in step 46 the counter state is set to zero after which the individual values 0 through n are gone through again starting with step 26 in fig3 a comb plate 2 with teeth 4 is shown the evaluation circuit 10 can also be seen the comb plate 2 has a conducting rail 48 from which individual conducting paths 8 branch each of which goes through a tooth 4 to the evaluation circuit 10 the evaluation circuit shown consists of or gates 50 and an and gate 52 the conducting paths 8 of each pair of two adjacent teeth go to an or gate 50 the outputs of the individual or gates go to an and gate 52 a test voltage is applied to the conducting path rail 48 the output of an or gate 50 is logically u201c correct u201d if the test voltage is present at one of the two inputs 54 56 of the or gate 50 this means that in case one of the two teeth 4 of a pair of adjacent teeth is broken the output signal of the corresponding or gate 50 is nevertheless logically u201c correct u201d only in case two adjacent.