15 i e the leading edge of the segment 11 and angular position u03b1 3 respectively the magnetic flux decreases while the space 13 now passes the receiving element 20 no substantial magnetic flux is generated in a manner analogous to segment 11 a change in the magnetic flux is now produced also by segment 12 at its leading edge as well as at its trailing edge i e at the angular position u03b1 4 and u03b1 5 fig2 c shows the pulses generated in the receiving element 20 a negative pulse is generated in each instance at the leading edge of the segments 11 12 i e at the angular position u03b1 1 and u03b1 4 the pulse is dependent on the polarity of the receiving element 20 when the receiving element 20 reaches the permanent magnet in angular position u03b1 2 another negative pulse is produced when the receiving element 20 reaches the rear flank of the segments 11 12 i e the transmitter disk 10 is located at angular position u03b1 3 and u03b1 5 a positive pulse is produced due to the magnetic field of the permanent magnet 15 the positive pulse at position u03b1 3 is greater than the pulse in position u03b1.