This
telephone was designed so that the users voice vibrated the diaphragm through
holes in the top of the transmitter housing while speaking directly into the
mouthpiece. Any unwanted loud noise entered the transmitter housing both from
the holes on top and underneath the diaphragm thus canceling itself out. The
dual swivelling receivers helped to block out the unwanted loud noise as well.
This desk set was found by the present owner in a second hand store in the town
of Mount Shasta, California. It is now part of the Christianson Telephone Collection.