In Captain F. J. Wylie's article, ‘Maritime radar automatic plotter display philosophy’ in the July 1974 issue of the Journal, he states that the IBM Maritime Application Bridge System (MABS) tracks only six targets for collision assessment purposes. This statement is incomplete and I would like to clarify the impression left with your readers.

The IBM MABS tracks up to 21 targets continuously while performing either automatic or manual acquisition. However, since the MABS also prioritizes targets according to threat potential (based on C.P.A. and T.C.P.A.), only the six most threatening are displayed continuously on the alpha-numeric data display and on the PPI. Should the operator wish to obtain data on the fifteen targets of lower priority he can request them in groups of six, in descending order.