Popular Science Monthly 



Japan's Commercial System of 

 Wireless Telephony 



ALTHOUGH it is not generally realized, 

 i Japan has been one of the most 

 diligent countries in making wireless tele- 

 phony a commercial possibility. The "T- 

 Y-K" radiophone system which the Japa- 

 nese have developed is unusual in simplicity 

 and compactness. It contains no very 

 intricate circuits, nor does it use a delicate 

 air-sealed spark-gap, as in other telephone 

 systems. The few adjustments that are 

 necessary can be made by almost anybody, 

 and the spark-gap will work while exposed 

 to the air, without deterioration. These 

 facts have .made the system so practical 

 that Japan has already established wireless 

 communication between her important 

 islands by means of it. 



The spark-gap electrodes are made of 

 oxide of iron, brass, aluminum, and similar 

 materials which are practically indestruc- 

 tible. The electrode surfaces are small and 

 are placed nearly 



155 



talking into the microphone transmitter. 



But all this depends upon the formation 



of a first spark which will release the charge 



of the oscillating circuit. The resistance 



Ground ' 



Diagram of connections: The transmitting 

 system uses an air-exposed spark gap. A 

 crystal detector system is used for receiving 



touching each other, 

 so that the spark- 

 producing potential 

 can be comparatively 

 low. Thus, the volt- 

 age of the exciting 

 generator is slightly 

 more than one hun- 

 dred, though as 

 much as five hun- 

 dred volts have often 

 been used. As soon 

 as a potential is pro- 

 duced across the 

 gap, an oscillating 

 circuit that is 

 coupled to the gap 

 becomes simultane- 

 ously charged. Once 

 a spark jumps across 

 the gap, the natural 

 tendency of both the 

 inductance and the 

 capacity of the oscil- 

 lating circuit is to send a current from one 

 to the other. The result is that each is 

 rapidly charged and discharged, the current 

 crossing the gap at a rate of about 120,000 

 times a second, producing one spark with 

 every surging. The surgings in the primary 

 circuit are then induced in the aerial and 

 microphone circuit which is coupled to it. 

 The result is that the aerial radiates its 

 wireless waves, which are modulated by 



between the two electrodes — caused by the 

 insulating layers of air and of the oxide 

 formed on the electrodes — ordinarily pre- 

 vents this. So an equilibrator is used for 

 temporarily raising the potential in the 

 spark-gap circuit. The equilibrator con- 

 sists of a strong electromagnet which, just 

 as soon as a current begins to build up in it, 

 attracts the armature of a circuit-breaker. 

 The circuit-breaker is sharply opened, and 

 the inductance discharges at high potential, 

 supplying the necessary potential across the 

 spark-gap. 



Since the equilibrator works auto- 

 matically, only the simple adjustments of 

 the oscillating circuits require attention. 

 The waves the system sends out, being of 

 relatively low frequency, can be received by 

 the ordinary crystal detector. Using it, a 

 maximum range of thirty to forty miles has 

 been obtained. 



A complete Japanese 

 T-Y-K installation 



A Crystal Detector Holder for 

 Wireless Apparatus 



A SIMPLE clip to hold the mineral con- 

 sists of a straight piece of brass sheet- 

 ing with a U-shaped piece of spring brass 

 soldered on at one end. Another and 

 better device for holding the mineral is a 

 reflector from an old tubular flashlight 

 of the larger size. Clean off the enamel and 

 polish up the brass. Fit a piece of wood into 

 the socket and drill a hole in it for a ma- 

 chine screw which passes through into the 

 base of the detector. A large brass washer 

 will be required under the head of the 

 machine screw. Drill and tap out three 

 holes through the side of the cup for the set 

 screws which clamp the mineral. The cup 

 will hold odd-shaped minerals of various 

 sizes and can be turned around at will. 



