Balmar Alternator D+ circuit

[SoonerSailor]

I understand what happens at the D+ terminal of a typical alternator - it allows current flow to ground for the alternator warning light circuit, and it does this via three diodes each connected to one of the three stator output leads.

On my Balmar alternator, there is instead a small circuit board with a single transistor, four smd resistors, and four diodes. This board is connected to a single stator output with one wire, and another wire goes to ground. And there is also the stud coming out of the board as the D+ terminal.

I wonder why this is done this way? I'm going to presume that if the board does not get AC from that single stator output, the transistor will conduct and bring the D+ terminal to ground.

Anyone know if this is correct, and why they chose to handle D+ in this fashion?

Thanks

[FPNC]

Call the Balmar technical help line

+1.360.435.6100 x3

They will be happy to explain the design.