the current threshold value detector id is connected to a control input of the controllable switch s which switches the inductor l u2014 the ignition coil u2014 on and off the second exemplary embodiment u2014 shown in fig2 u2014 of the timing circuit according to the invention will now be described and explained the construction of the current threshold value detector id is shown in the second exemplary embodiment of the timing circuit according to the invention shown in fig2 the electric circuit contains the voltage source u the controllable switch s the inductor l and a measuring resistor r to whose connections a voltage threshold value detector ud 1 is connected the measuring resistor r and the voltage threshold value detector ud 1 form the current threshold value detector id the second exemplary embodiment can also be used in an electronic ignition system a control output of the voltage threshold value detector ud 1 is connected to the control input of the controllable switch s which switches the ignition coil l on and off the third exemplary embodiment of the timing circuit according to the invention the third exemplary embodiment being incorporated in an electronic ignition system and is shown in fig3 will now be described and explained in fig3 one connection of a primary winding pw of the ignition coil l is connected to one pole of the voltage source u u2014 the vehicle battery u2014 and a first input of a second voltage threshold detector ud 2 a second connection of the primary winding pw of the ignition coil l is connected to the second input of the second voltage threshold value detector ud 2 and to a collector of a field effect transistor t which constitutes.