Nikon Strobe Info

I extracted the following from a Nikon support document

The following strobes support these modes on the D200, D80, D70s, D70, D50, D40

SB800
i-TTL, Auto Aperture (AA), GN, Auto, Manual, Rear Curtain, Repeating Flash, Red-Eye Reduction, AF, Zoom

SB600
i-TTL, Manual, Red-Eye Reduction, AF, Zoom, Rear Curtain

SB400
i-TTL, Manual

i-TTL
The camera controls flash output. This is a TTL auto flash mode in the Creative Lighting System. Monitor Preflashes are fired at all times. The subject is correctly exposed by the light from the flash and the exposure is less affected by the ambient light than in the conventional TTL mode.
Supported cameras: D2X, D2Xs, D2H, D2Hs, D200, D70, D70s, D50, D80

i_TTL as described in Nikons CLS document
Monitor pre-flashes are emitted from a Speedlight before the main flash and reflected off every object in the frame. Monitor pre-flashes are picked up by either the five-segment TTL flash sensor or an RGB sensor. This information, along with data from the Matrix Metering System is analyzed to adjust flash output for the most balanced background/foreground exposure possible.