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The ¡°free-space¡± position and coordinate system are defined as follows:
1. Ready the EUT for operation, if necessary.
2. Define two imaginary lines on the EUT: the vertical centerline and the horizontal
line. The vertical centerline passes through two points on the front side of the EUT:
the midpoint of the width wt of the EUT at the level of the earpiece (point A on
Figure A-1), and the midpoint of the width wb of the bottom of the EUT (point B).
The horizontal line is perpendicular to the vertical centerline and passes through the
center of the earpiece (see Figure A-1). The two lines intersect at point A. Note that
for many EUT's, point A coincides with the center of the earpiece, however, the
earpiece may be located elsewhere on the horizontal line. Also note that the vertical
centerline is not necessarily parallel to the front face of the EUT (see Figure A-1),
especially for fold EUT's, EUT's with flip pieces, and other irregularly-shaped
EUT's.
3. Define a Cartesian coordinate system with the origin at point A, where the positive
Z-Axis is along the line from B to A, the positive Y-Axis is along the horizontal line
and points to the ¡°right¡± of the phone face, and the positive X-Axis is orthogonal to
the Y-Z plane and points away from the face of the phone. Figure A-2 illustrates this
coordinate system definition for three typical case styles of EUT. In all cases, the
longitudinal direction of the EUT is the Z-axis, and the right hand rule is used to
define the X- and Y-axes.