Miller: I don't question that transducers were known in the late 1920's but I do question whether they could be used for pressure and time measurement at that time. Beginning around the start of WWII, the oscilloscope had been developed which could be used to show both an electrical pulse and a time line when hooked up to a piezeo crystal, but I don't know how the output of a crystal transducer would have been displayed before that time.