Found a nice on-line source from the University of North Texas, Digital Library. They have an on-line copy of FM 6-135, Field Artillery Forward Observation, for that half of the off-board support systems. Starting on page 37, they describe appropriate terminology. On page 39, it covers "REPORTS TO OBSERVER," with example: "TIME FIRE, CONCENTRATION 27, BATTALION, ABLE, 3 VOLLEYS, 1/2 c APART, WHEN READY."