Telephone as an Oscillograph. 913- 



'ig. 6 is registered by means of an ordinary telephone 

 Fior. 6. 



-^ 



from L. M. Eriksson Telephone Comp., Stockholm. Fig. 7 is 

 taken by means of the same telephone but with a thinner 

 membrane. Both these figures show that the free vibrations 



Ffe. 7. 



S ^gggv^^**^ ^ 



s 



must be suppressed, in order to render a true reproduction 

 possible. To enable us to see whether an electromagnet in 

 damping might diminish the free vibrations, a copper-plate 

 (2 mm. thick) was laid upon the membrane with a thin leaf 

 o£ mica between them. But, as shown in fig. 8, the damping 



Ficr. 8. 



< & 



obtained was, however, insufficient. Then a mechanical 

 damping was tried. The entire telephone was filled with 

 The corresponding registration is reproduced in fig. 9. 



on. 



Fig. 9. 



The result of all this is, that the telephone is not practicable 

 for oscillographic purposes if the registering curves show such 

 rapid variations. 



