Yes, B210s have a low-fluid-level warning sensor. skinnykid, do you have a newer ute? The 1971-1973 Datsun 1200s don't have a level sensor.

So that the fluid level problem B210sleeper mentioned doesn't occur, you can manually adjust the rear brakes every 6-12 months. The pedal should be high and tight, with little play. Datsun 1200's have an excellent pedal feel (at least the disc brake models do).