Ignition Control to Distributor

Yeah the pickup coil will have 1 end connected to a ground that is chosen as ground by the module. it may be slightly above chassis ground to avoid interfernace from the regulator igntion or diodes switching in the alternator.

it acts as the 0 line in the diagram i posted
signal plunges lower than this ground and then swings higher than this ground.
better called 0 volts as i don't know if its the same as chassis ground.
so that the module can tell when it is positive enough to be considerd trigger voltage. it needs a 0V in order to act as a comparison to what it sees from the pickup which will be lower than 0 v then higher than 0v. as a metal tooth approaches and then retreats from the pickup.


transistors and similar are just an electronic switch. or think of it like a Tap in a pipe. middle pin is the switch or tap handle and depending on type the transistor switches a flow of current through the other two pins on or off
most switches you just flip a lever with a transistor you apply 0.6V or more to the middle pin and it switches on or off....depending on type.... i.e the middle pin is the tap handle on the pipe between bottom pin and top pin. transistor is basicaly two diodes back to back with their annodes or cathodes joined. you can check em with your multi meter.
you should see high resistance between middle pin and top pin with the leads 1 way and low resistance the other. the situation should be mirrror image for the middle and bottom pin with the trsnsistor on the bench. low resisistance setting please do not blast it with 15 volts.
NPN transistor will do exact oposite of a PNP transistor hence my talk of OFF or ON

so in the module i would imagine a small transistor and potential divider as part of the trigger circuit used to switch on or off the big power transistor that controls coil current. keep the sensitive low amp stuff away from the big amps.
like controling your headlamps with a relay to save your hedlamp switch.

The switching voltage + bias voltage that is at the middle of the potential divider set by the two resistor sizes will be enough to trigger the small trigger circuit transistor to switch a voltage on that is more than the switch on/of volts into the middle pin of the BIG transistor which controls the coil.

i'll have a look at the schematic later so at the mo. this is just a basic guess.
the real circuit will have lots of control and compenstation parts to take into account frequency, heat, variation in pickup coil, and depleating magetism in the pickup etc.

the forerunner to the transistor was the Valve (europe) or Tube (in USA speak) hence the tap anaology which is totally wrong in electrical terms but works well for understanding is going on. :)

a triode tube would be used in the old days where we use to a basic transistor today. the russians used tubes in weapons systems fighter jets and space flight until the early 2000s. tubes are not killed by the electro magentic storm caused by a nuclear blast, transistors and chips are.
Or indeed as many have found out, killed by a faulty alternator.

Dave