Whelen Traffic Advisor Plug Question

[Watermelons are cool]

A quick question on the Whelen TA plug connections, like the one that interfaces with the Whelen TACTL5. So my understanding is that pins 1-8 are to the power/positive wires of the dummy style lightheads in TAs, and the grounds go to y'know, chassis ground? But then there is pin 9, just labeled as "+BATTERY". Where does this 9th wire come from with only 8 positive and 8 negative wires. I'm probably just severely misunderstanding something somewhere. Below is a screenshot from the Whelen TACTL5 PDF and a hastily done diagram from my understanding that is likely wrong.

 

[firebuff17]

I believe that the 8 colored wires that coincide with each lamp are the grounds. And the white wire labeled +Baterry is power/positive. The TA is negative switched.

 

[Watermelons are cool]

Ah, alright. I'm far from an electrician.. hence the post. Does the positive wire 9 just splice all 8 lighthead positive/power wires into one (if you know)?

 

[firebuff17]

Yes. “Should” be internally connected to all 8 heads from the factory.