Audio Systems: Car radio antenna, car radio antenna, caution notice

Question
I just saw a caution notice on the device. It says: CAUTIN +12V DC Negative Ground. What is this? Never heard of it...

Answer
Most car systems now days have the negative terminal of the battery connected to chassis ground.  

That makes all the voltages in the car at 12v +.

There are, still, some cars (especially from Europe) that have the positive terminal of the battery grounded; making all the voltages of the vehicle 12v negative.

What is means it the antenna is for postive voltage systems only and should not be used in other systems.


Cleggsan