for Lucas 22D, 23D, 25D distributors, positive earth cars only
The Newtronic contactless electronic Ignition system uses an optical trigger to energise the coil. A slotted disc fitted over the distributor cam revolves between an infra red light emitting diode and a photo transistor. As the slots in the disc alternately expose and cover the light they activate the photo transistor which in turn triggers the electronic circuitry to switch the coil and produce a spark. At high speeds, the disc system allows up to three times longer for the coil to charge than is available with a contact set system. This ensure a powerful spark even at high speed. Another important feature of this system is that there are no contacting moving parts so wear and tear are eliminated and the timing stays accurate for an indefinitely long period.