Showing Alternator Internally
When the Slip ring brushes pass the Stator windings, an Alternating Pulse is created. These pulses are then passed to the Rectifier diodes. They in turn pass a DC voltage to the battery via B+ for charging.
The ignition switch supplies a voltage to the Brushes & slip rings to initiate a voltage which will give an imputus to the magnetic windings to create a voltage.
When the status windings produce a voltage this then produces a back voltage to the Dash ignition lamp which is then turned off.
Sometimes the diodes go 'Leaky' and allow a current path for the Ignition lamp causing it to glow at a low level.
The W contact produces an AC waveform and is used for Tachometer functions.