WIRELESS TELEPHONY—SLAUGHTER. 181 
during the war, but furnishes also a remarkable example of the 
rapidity with which the engineering and manufacturing facilities 
of this country were adapted to war-time needs, a detailed summary 
of the development, production, and operation of this set forms an 
important part of the general subject of wireless telephony. 
HISTORICAL REVIEW. 
Almost immediately following the declaration of war by this 
country the Chief Signal Officer of the Army issued orders for the 
development of an airplane wireless telephone set which was to 
furnish telephone communication between the different airplanes of 
a squadron and also to furnish communication between an airplane 
and a ground station. The fundamental requirements for this set 
were based partly on information furnished by the Allies and partly 
on the experience of the United States Signal Corps in the prewar 
experiments in airplane radio telegraphy and telephony. The actual 
development work was intrusted to the engineering department of 
the Western Electric Co., with provision for the necessary airplane 
facilities and information to be supplied by the Signal Corps as 
required. The progress of the development work was extremely 
rapid, successful communication being established between an air- 
plane and a ground station within six weeks from the date the de- 
velopment was started. The evolution of a complete design suited 
to commercial production likewise proceeded very rapidly, so that 
by December, 1917, only six months from the time the development 
work was started, the design of the complete equipment had reached 
the stage where production of the sets in quantity could be author- 
ized. As early as October, 1917, the apparatus had been developed 
to a sufficiently complete extent to warrant sending samples to the 
expeditionary forces for test under conditions existing at the front. 
Because of the extreme need for the earliest possible delivery of 
apparatus in large quantities to meet the needs of the airplane pro- 
gram of the United States the production of airplane telephone sets 
was begun prior to the completion of the experimental work. As 
further experiments indicated the need of modification or refine- 
ments in the design the necessary changes were incorporated in the 
process of manufacture, so that the sets delivered in the spring of 
1918 embodied the results of experimental work extending almost 
up to the date of completion of the sets. 
Beginning early in the summer of 1918 the development of an 
improved type of set was begun, and at the time of the armistice 
this development had reached the point where practical trials of 
the completed sets were in progress. The essential differences be- 
12573°—21——_18 
