Linear Technology LINEARCOM3000 LC3.IRTX Operation Manual page 8

If the path of the infrared signals is blocked, e.g. under balconies, at least one additional
radiator is needed to cover the 'shaded' area.
Overlapped footprints and multi-path effect
If footprints of two radiators overlap, the total coverage area maybe larger than the sum of
the two separate footprints. In an area with overlap effect, the individual radiation signals of
two radiators are added, resulting in an increase of the radiation intensity, larger than the
required intensity.
However, due to the differences in the delays of the signals from two or more radiators,
the signals may cancel out each other (multi-path effect). In a worst-case situation, loss of
reception at some positions (black spots) may be the consequence.
8