Abstract: An arrangement and a process for communication between an ignition module (ICM) mounted on an engine and a control unit (ECM). The ignition module includes detection circuits and signal processing stages in order to determine at least one combustion related parameter from detected ionization currents in the combustion chamber (22). The control unit (ECM) communicates with the ignition module via at least one bi-directional communication wire (K.sub.CQ or K.sub.KI). Via the communication wire the control unit activates the detection in the ignition module, and the ignition module sends a signal corresponding to the magnitude of the detected parameter to the control unit on the same communication wire. Activation and transfer of parameter data is conducted sequentially over the communication wire.

Abstract: A measuring circuit for sensing ionization within a combustion chamber of an engine is arranged in the grounded end of the secondary winding (5) of an ignition coil (2), and includes a voltage source for measurements having a substantially constant potential. The voltage source for measurements used is a capacitor 13 which is charged by the spark current SC, and subsequently after the ignition spark goes out will apply a bias voltage over the spark plug gap 3 with a reversed polarity in relation to the spark voltage. The ionisation within the combustion chamber is detected with a measuring resistance 14 arranged in series with the capacitor 13. A rectifying element 11 is connected in parallel with the measuring resistance, which will secure that the spark current is developed in the spark plug gap 4 and that the measurement current passes through the measuring resistance 14. The rectifying element is grounded with a separated ground strap which does not pass the ground plane of the measuring resistance.

Abstract: Apparatus for sensing the relative position between a fixed first machine component and an axially displaceable and pivotably mounted second machine component includes first and second bar-shaped magnets disposed at mutually right angles and rigidly connected to the second machine component, each of the magnets having a free pole; and a plurality of transducers rigidly connected to the first machine component and facing the free poles of the magnets for sensing the magnetic field of said magnets. At each long side of each of the first and second magnets an adjacent magnet disposed in parallel with the respective first or second magnet, each of these adjacent magnets having a free pole disposed in the vicinity of the free pole of the respective first or second magnet. The free poles of the first and the second magnets have a polarity reverse to that of the free poles of the adjacent magnets, and each magnet has opposite to its free pole a second pole directed away from the transducers.