Vibration recorder

W. F. Davidson: Some time ago, I had occasion to consider the possibility of carrying on measurements of about the type described by Mr. Mershon and looked into the possibility of several methods, but we seemed to run into difficulties because the vibrations that we wanted to record were in the order of 200 cycles. Modulating a 500-cycle wave with 200 cycles does not give a very satisfactory wave to work on. On the other hand, using frequencies higher than 500 cycles is likely to lead to some circuit difficulties, especially if an oscillograph is to be used. I have wondered whether it might be possible to use frequencies in the order of several thousand cycles and then, through a valve arrangement similar to a radio detector circuit, unscramble the composite current so that the wave can pass through the oscillograph and reproduce truly the original modulating action. It seems to me that there is a possible development of considerable value in this direction.