AN OSCILLOGRAPH FOR TEN THOUSAND CYCLES 



85 



it also provided for developing the paper immediately after exposure, 

 the rate of development had to be slower than that of exposure because 

 of the very high speed of the paper necessitated by the higher fre- 

 quencies recorded. 



SHADOW OF STRING 

 CLUTCH ROLL 

 CYLINDRICAL LENS 

 VIEWING SCREEN - - 



PROJECTING 



CONDENSING 

 LENS 



FIXING TANK 



STORAGE TANK 



Fig. 11 — Diagrammatic arrangement of the new rapid record oscillograph. 



This improved instrument, christened the rapid record oscillograph, 

 proved greatly superior to other available equipment and has been 

 used extensively in the varied work of Bell Telephone Laboratories. 

 Recently the galvanometer of this oscillograph has been redesigned, 

 employing the electrical methods of equalization already discussed, 

 and in its present form has a frequency range extending up to ten or 

 twelve thousand cycles per second. With this new equipment most 

 of the components of speech and music may be recorded. 



Its arrangement is shown in the schematic photograph of Fig. 11. 

 Light from the lamp at the left is focussed by the condensing lens on 

 the strings of the instrument through the perforated pole piece. Only 



