Popular Science Monthly 



783 



sparks will pass from the normal opera- 

 tion of step-up transformer i. When 

 surges are set up in the lines 3 by the 

 operation of the distant wireless trans- 

 mitter, the impulses serve to increase 

 the potential of the secondary 5 and a 

 series of sparks passes across 6. This 

 results in a stronger charge being placed 

 upon condenser 8, ii, 10 and the plates 

 are therefore attracted more strongly 

 than before. By the ensuing motion of 

 21 and 19 the contacts 18 and 15 are 

 brought together, the local current flows 

 and the sounder or recorder is operated. 

 As soon as the key of the sending 

 station is opened, sparks cease to pass 

 across 6, plate 10 swings back to its 

 normal position, and the sounder circuit 

 opens. Thus, it becomes possible to 

 observe the transmission of wireless 

 messages from a station in the vicinity 

 without using an antenna or detector in 

 the usual way. It is not always neces- 

 sary for the instruments described to 

 be connected with the power line supply- 

 ing the wireless station, for often the in- 

 ductive effects are sufficiently strong 

 to operate such an apparatus located 

 at a considerable distance from the 

 signaling plant. 



Magnetic Adjustment of Audion 



A UNITED STATES patent issued in 

 1915 to B. Graves, No. 1,138,652, 

 shows an interesting method of con- 

 trolling electromagnetically the action 

 of an audion receiver. The diagram of 

 that patent is reproduced, in which the 

 usual complete receiving-circuits are 

 shown. The new features are the coil 

 of wire 25 wound about the bulb and 

 connected to battery 23 through regulat- 

 ing resistance 24, and the electromagnet 

 20, which is supplied with current from 

 battery 21. By varying the position 

 and strength of the magnet 20, and by 

 altering the intensity and direction of 

 current through the coil 25, the patentee 

 has found it possible to increase the 

 sensitiveness of his audions. The matter 

 of magnetic control of such receivers is 

 of considerable experimental interest, 

 and it is doubtless well worth while to 

 try this method. 



The consensus of opinion on the 

 matter, however, so far as there is any 

 agreement, seems to be that any effects 



which can be produced magnetically 

 may also be secured by variation of 

 filament current, plate circuit potential 

 and tube vacuum. Occasionally it is 

 not found possible to get the best re- 

 sponse from a given bulb by any of the 

 ordinary adjustments, and in these 

 instances full sensitiveness is sometimes 

 secured by applying a properly-disposed 



Increasing the sensitiveness of the audion 

 with an electromagnet 



magnetic field. The inventor of the 

 method shown, states that by its use 

 he has secured better results than from 

 a simple magnetic field set up by a 

 permanent magnet. It is probable 

 that the independent control of magnet 

 position and field intensity makes it 

 possible to secure the best conditions 

 more easily. 



Learning the Code 



AMATEURS learning the Continen- 

 tal code will find it a great help to 

 practise sending and receiving words 

 which necessitate the use of letters 

 frequently misunderstood or forgotten. 

 The prime essential in learning the code 

 is to forget how each letter looks on the 

 code chart and learn to recognize the 

 letters by sound. Such letters as F, 

 L, Y, Q, X, and others have a peculiar 

 rhythmic sound which soon becomes 

 familiar and easily recognized. The 

 following words are helpful in code 

 practice: fizz, fall, calf, fix, lax, liquor 

 lacquer, buzzer, squall. 



Telephone Receivers 



FOR long distance receiving, a good 

 pair of head telephones is always a 

 profitable investment. If the telephones 

 are insensitive, it is useless to expect to 

 hear distant stations. 



