Abstract: A system for detecting rotational frequency of engine which comprises a switching device including a switching transistor for switching on and off the flow of current to the ignition coil of an internal combustion engine and a current limiting circuit for limiting the flow of current to the switching transistor to a predetermined value, and a speed detecting circuit connected to the junction of the ignition coil and the switching transistor.

Abstract: A high tension generating and distributing device includes a plurality of secondary windings 11, 12, connected to associated ones of the spark plugs of an internal combustion engine, these secondary windings being mounted on a single magnetic frame 1, 2 offering a plurality of flux paths through a low tension primary winding 7 or 8, each of these flux paths being associated with one of the secondary windings 11, 12 and with means, for example in the form of flux gaps 3, 4, 5, 6 or auxiliary windings 213, 214 having associated therewith shunt switches 215, 216, for limiting or cancelling the magnetic flux in some of the flux paths so as to leave one flux path with a higher rate of change of flux than the attenuated rate of change of flux in the other flux paths, thereby selecting the secondary winding associated with the non-attenuated flux path as the one in which the high tension current is to flow.

Abstract: The invention provides a distributor device for H.T. supply to an internal combustion engine, and comprising several ignition coils and a single contact breaker to interrupt supply to one or more of those coils at any instant, each of the coils having its primary winding shunted by a thyristor which can be controlled to select whether the primary winding of that particular coil is to be energized, or not, as the case may be.In one embodiment, the thyristors are polarized so as to conduct in a direction allowing "idling" circulation of current through the closed circuit comprising the shunting thyristor and its associated primary winding; in another embodiment the thyristors are polarized in the reverse direction and a diode is connected between the gate and the cathode of each thyristor to protect the cathode from gate voltage and another diode is connected to protect the gating circuit of that particular thyristor.