How do Taillight Converters work??

Hi,
I am working on a little project for automotives and for this I need to split Turn and Stop signal.
On many US cars the Turn and Stop light signal uses the same wire at the taillights. So you got 3 wire.
- GND
- Parking Light
- TURN / STOP LIGHT

Now I need to split the TURN and STOP light, but I dont know how to do this. And I dindt thought it is even possible until I have seen this thing.

http://www.redtrailers.com/ShowItem.asp?id=118158

I really would like to know hoe they can decide if it is a turn or a stop signal?
Do they just check if left and right TURN/STOP signal is high and they say it must be STOP Light? But what if I use my hazards?

thanks and best regards

From your post I think you have already figured it out.
Stop=left AND right OR (Oneshot(left and right) AND (left OR right))
Left_turn = left AND /right
right_turn = right AND /left

Hazard will blink the Stop bulbs.
An easy project that you can build for a few bucks worth of parts.
Have fun.

BTW - if you are not familiar with the oneshot function it can be implemented with a LM555 timer.

OK, So it is a really easy electronic.

So I think the easiest way to make sure it really is the brake signal i just run a signal wire from the high mountes stop light.
Then I really know for sure when it is the STOP Light

Sorry, I do not know what the high mountes stop light is.

Running a wire may or may not be simpler - it depends on access.

If all you want to do is get your trailer lights to work properly why not just cut the common power connection between the two stop bulbs and tie each one into the turn indicator circuit on their respective sides, that way you have converted a 4 wire system to a three wire system.

high mounted stop light is the third brake light.

i need to convert from a 3 wire system to a 4 wire system

Thank you for the explanation - I learned what a high mount is.
Sounds like what you suggest will work however building a converter would be straight forward if you were looking for a little project to do.