Abstract: A transducer responsive to a plurality of different parameters includes a plurality of sensing devices responsive to the parameters and arranged to combine two signals in relative proportions dependent upon the value of the parameter concerned. The two signals have the same frequency characteristic and are switched cyclically between different relative phases; typically the signals are switched between an in phase condition and a quadra-phase condition. A processing circuit is provided which compares the output of the different parameter sensing devices when the signals are in phase and in phase quadrature so as to derive output signals indicative of the values of the different parameters which are free of phase errors that would otherwise impair the output signals.

Abstract: An ignition system for an internal combustion engine which includes circuitry for generating a pulse of a duration which is substantially independent of engine speed within at least a predetermined speed range. Means are provided for varying the timing of said pulse at least in response to engine speed (and, in the preferred embodiment described, to load as measured by manifold vacuum) so that the end of the pulse occurs at the required angle in the engine cycle, in accordance with engine speed and possibly other inputs.In the preferred embodiment described, a read only memory stores engine angle signals which are converted into an appropriate delay by means of a programmed delay line.Means are also provided in the pulse generation circuit for protecting the components thereof from high overswing voltages.

Abstract: A signal combining circuit includes means for receiving a pair of digital waveforms of similar frequency and for producing a further waveform which is indicative by its phase of the relative amplitudes of the waveforms. A circuit arrangement is provided for reducing undesirable distortions of the shape of the further waveform, however this arrangement introduces undesirable phase modifications and means are provided for reducing the effect of these modifications. The relative phases of the two digital waveforms are, at a predetermined frequency, switched to one or other of two predetermined relationships and the phase of the further waveform obtained when one of the relationships occurs is compared with that obtained when the other relationship occurs in order to compensate for said modifications.