Page:Popular Science Monthly Volume 88.djvu/811

 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.

�� �