All about U1
Design of an NGK Distributor Ignition Coil
In order to prevent electric discharge and spark-overs in the interior of the coil or outward, the wires of the primary and secondary coils must be insulated.
This is ensured by the quality of the winding and the mould compound.
A high-quality winding of the coil can be seen in the cross-section, where the wires are precisely arranged above one another, so that there is no recognizable spacing between them, winding ratio for ignition coils is normally 1:150 to 1:200.