Nikon D70/D70s Users Guide
FLASH SYNC MODES
Select these by holding down the flash button on the left side of the flash hump and spinning the rear dial. Your selection is shown on the top LCD in the box with the bolt.
Normal (blank, which is the default): In Program and A exposure modes, the shutter won’t stay open longer than about 1/60 second. You can change this minimum speed in custom function 21, which defaults at about 1/60 second. I forget the exact default because I have mine set to 1/15.
In this mode you won’t get blur indoors, but you may not get more than a very black background either. Choose a longer speed, like 1/8, in CSM 21 to lighten the backgrounds indoors, but watch for motion.
I usually use Normal mode, since if I don’t I can get some scary long exposures if I’m not expecting them in the dark.