THE WORLD'S ADVANCE 



391 



Schematic Drawing of a Telephone Receiver of New Design, as well as Diagrams of the Magnetic Cir- 

 cuits and their Effects on the Diaphragm at Different Periods in its Operation. 



the lower U-shaped pole piece, longitu- 

 dinally through the armature and 

 through the left hand branch of the 

 upper U-shaped pole piece to the upper 

 end of the permanent magnet, and thence 

 through the permanent magnet to the 

 other end. In this case the armature is 

 rotated in the opposite direction on its 

 pivot and transmits to the diaphragm 

 a movement in the opposite direction to 

 that in the previous case. 



The extreme sensitivity of the new 

 receiver is probably due to two causes: 

 First, that the diaphragm is at all times 



when not acted upon in nowise deflected 

 and therefore as in the case of a spring 

 is easier to deflect than a diaphragm 

 which is under constant strain as in the 

 ordinary types of receiver. Secondly, 

 that the armature is acted upon at both 

 ends and the flux is produced differen- 

 tially, a very similar action to that ex- 

 isting in a polarized relay. 



The receiver is undoubtedly more del- 

 icate than standard types, but, it is 

 claimed, owing to its great sensitiveness, 

 it will probably be widely adopted in 

 wireless work. 



CONTAINERS FOR WIRELESS 

 INSTRUMENTS 



Serviceable cases for condensers, test 

 buzzers and other wireless instruments 

 can be easily made from cigar boxes. The 

 labels of the boxes can be readily re- 

 moved by thoroughly moistening them, 

 followed by scraping. The top and bot- 

 tom of the boxes are apt to warp but 



this can be prevented by gluing across 

 the inside small strips of wood. 



For large fixed condensers, the cigar 

 boxes used as containing cases can be 

 filled with melted paraffine. This will 

 insure good insulation. In the case of a 

 test buzzer the noise can be materially 

 lessened by packing felt, waste or excel- 

 sior around the buzzer. JOHN B. RA- 

 KOSKI. 



