WIRELESS TELEPHONY — SLAUGHTER. 189 
any other phase of airplane wireless telephony. This is partly due 
to the fact that the form of antenna above described possesses ex- 
tremely efficient radiating properties and partly to the fact that 
investigations of the subject require very extensive and painstaking 
measurements involving actual flights of airplanes. The investiga- 
tions conducted during the war, however, included a large number of 
tests of various types of Antenna, the principal object of which was 
to evolve a substitute for the long trailing wire which would be better 
adapted for use on airplanes engaged in acrobatic flying. Obviously 
the movements of an airplane were somewhat restricted by the use 
of this type of antenna. 
Without indicating in detail any of the alternative types of an- 
tenna which were developed and used it may be stated there are a 
number of forms of airplane antenna which offer considerable promise 
of complying with the radiation requirement and at the same time 
offer practically no interference with the movements of the airplane. 
The tactical uses of the airplane wireless telephone called for trans- 
mission and reception on certain airplanes and for reception only on 
other airplanes. The apparatus developed therefor included two 
distinct types, one including both the transmitting and receiving ele- 
ments mounted in a single box, as shown in plate 2, figure 1, while 
the other included only the receiving element, as shown in plate 2, 
figure 2, and plate 3. The complete equipment comprising the 
transmitting and receiving set is shown in plate 4. The complete 
equipment comprising the receiving set only is different with respect 
to the power plant, which in this case consists of a 4- volt storage bat- 
tery. This figure shows two telephone transmitters and two helmets, 
which are used in connection with an interphone system provided as 
an auxiliary to the wireless telephone. This interphone system en- 
ables two persons in the same airplane to converse with each other by 
ordinary telephone, and furnishes in itself a valuable communication 
system entirely exterior to the wireless telephone apparatus. 
Where communication between an airplane and a ground station is 
desired this communication is effected by means of a special ground 
set which has been developed to correspond with the range and wave- 
length requirements of the airplane apparatus. 
In using the apparatus above described, the only manipulation re- 
quired of the aviator is switching from the transmitting to the receiv- 
ing apparatus, or vice versa, as required. Eanges of several miles be- 
tween planes are easily accomplished, and under extremely favorable 
conditions much greater distances have been covered. 
