WIKELESS TELEPHONY PESSENDEN. 183 



circuit for hours at a time. Plate 12, figure 1, shows a modified form 

 with split back. 



Plate 12, figure 2, shows a transmitting relay for strong currents. 

 The only thing noticeable about this is that the telephone magnet is 

 a differential one. 



Plate 13 shows a type of condenser transmitter in which the vibra- 

 tion of the diaphragm alters the electrical capacity of the transmitter, 

 thus throwing the circuit in and out of tune or spilling more or less 

 energy through a leakage circuit. 



Plate 14, figure 1, shows another type of transmitting relay for 

 amplifying very feeble currents. It will readily be understood that 

 where a person in Albany, for example, wishes to talk to another 

 person on board a ship off New York, the wireless station being 

 located near New York, the volume of the transmission received at 

 New York will not be very strong, and while it may be possible to 

 transmit it without amplification, amplification is advisable. 



This receiver is a combination of the differential magnetic relay 

 and the trough transmitter. An amplification of fifteen times can be 

 obtained without loss of distinctness. The side electrodes of the 

 trough are water jacketed. The successful amplification depends 

 upon the use of strong forces and upon keeping the moment of 

 inertia of the moving parts as small as possible. Amplification may 

 also be obtained by mechanical means, but as a rule this method 

 introduces scratching noises, which are very objectionable, even 

 though comparatively faint. 



Other tj^pes of transmitters have also been used, such as liquid jet 

 transmitters, transmitters operating by closing the air gap in a mag- 

 netic circuit (plate 15, figure 1), and so changing the inductance of 

 the oscillating circuit, etc. 



Plate 14, figure 2, shows a loud-speaking telephone receiver. A 

 small iron disk is placed opposite a nozzle through which air at high 

 pressure is blown. As is well known, this causes the disk to be held 

 close to the nozzle. The telephone magnets alter the position of the 

 disk and thus produce very loud talking. 



The transmitting relays are connected in the wire-line circuit in the 

 same way as the regular telephone relay, except that in place of being 

 inserted in the middle of the line they are placed in the wireless 

 station and an artificial line is used for balancing. There is no diffi- 

 culty met with on the wireless side of the apparatus, but on the wire- 

 line side there are the well-known difficulties due to unbalancing 

 which have not yet been entirely overcome. For the correction of 

 these difficulties, therefore, we must look to the engineers of the wire 

 telephone companies. At present the difficulties are, if anything, less 

 than those met with in relaying on wire lines alone. 

 88292— SM 1908 13 



