TWO AND ONE CONFIGURATION

Two and One configuration

The highlighted cell draws your attention to the pattern cell containing a 2. This cell requires two lamps, but has three vacant adjacent cells. We need to determine which of the three will contain the lamps. The diagonally adjacent pattern cell containing a 1 gives us the answer. Of the two cells C2-R6 and C3-R5, only on is permitted to contain a lamp, thus forcing the highlighted cell to contain a lamp.