Provides the number of the Paper Handling Device that
contains this input tray.
Additional information:
The internal trays belong to device 0 (base engine), the
envelope feeder is considered to be device 1
and the external input devices can number
between 2 and 6 depending on individual user
configurations.
NOTE: only TRAY6 and TRAY7 are listed here
because HP does not make a device with more than
two trays, but the Specification requires
support of up to 10 external trays. Therefore the
objects for TRAY8-PHD ... TRAY15-PHD will exist if
that many trays exist.