Popular Science Monthly 

 Making Telephones and Pho- 

 nographs Speak Perfectly 



A TELEPHONE receiver for 

 reproducing the sounds of 

 the talking voice without any of 

 the hissing, spitting and scratch- 

 ing that now accompany tele- 

 phone conversation, is an in- 

 vention of Erik Christian Bayer, 

 of Denmark. 



This receiver works on an en- 

 tirely new principle. Instead of 

 a single sound-producing dia- 

 phragm, his device uses a num- 

 ber of wires. These wires vary 

 in length much like those of a 

 piano, and each wire produces 

 its own fundamental tone. And 

 like the wires of a piano, they 

 vibrate with different 

 strengths and thus produce 

 other complex sounds. In this 

 way, the reproduction of voices 

 is obtained. By eliminating 

 those wires which would produce the sing- 

 ing and other noises in the telephone line, 

 these foreign sounds are entirely excluded 

 from the transmission. 



By connecting the ordinary phonograph, 

 through a telephone transmitter, with this 

 novel receiver, Bayer hopes to strain out 

 all impure secondary sounds — even the 

 scratching of the needle itself. 



This application of the idea although 

 simple, does not seem practical, however; 

 for it is only reasonable to infer that the 

 impure sounds that might possibly be in- 

 troduced by the transmitter would be 

 almost if not equally as annoying as those 

 weeded out. The photographs below show 



745 





The form is moved 

 along from section to 

 section of the wall. 

 There is no waiting for 

 the concrete to set. It 

 is possible to erect 

 three or four ten-inch 

 courses during a day 



A 



the diagram and application of the device. 



Source of direct current 



Any Boy Can Build a Concrete Wall 

 with This New Metal Form 



WISCONSIN man has invented a 

 new type of metal concrete form for 

 constructing hollow or solid concrete walls. 

 The supporting frames of the form are 

 rigid while the arms supporting the mold 

 boards are of flexible spring steel which 

 prevent the form from bending out of 

 shape. The rigidity of the form makes it 

 possible to erect walls true and straight. 

 Fresh concrete is spread into the mold 

 and tamped down until the mold is com- 

 pletely filled. Then a lever is raised which 

 releases the machine from the wall. The 

 form is moved along and another section of 

 the wall is formed. 

 There is no waiting for 

 the concrete to set. It 

 is possible to erect 

 three or four ten- 

 inch courses in a 

 day. 



The expense and 

 waste of lumber in 

 building forms 

 is done away 

 with. Bytheaid 

 of this form any 

 novice can erect 

 cement walls for 

 buildings or 

 partitions. 



The electric current going through the 

 wires, vibrates them and produces the 

 voice sounds. All wires that would set 

 up other sound vibrations are inactive 



