Combination amplifier, oscillator and filter

Claim 1

VIBRATION ANALYZING APPARATUS COMPRISING A DEVICE FOR CONVERTING MECHANICAL VIBRATIONS INTO AN ALTERNATING CURRENT SIGNAL HAVING A FREQUENCY PROPORTIONAL TO THE FREQUENCY OF THE VIBRATIONS AND AN AMPLITUDE PROPORTIONAL TO THE MAGNITUDE OF THE VIBRATIONS, A SIGNAL AMPLIFYING DEVICE, MEANS FOR APPLYING SAID ALTERNATING CURRENT TO SAID SIGNAL AMPLIFYING DEVICE, A POSITVE FEEDBACK PATH FOR THE AMPLIFYING DEVICE, A NEGATIVE FEEDBACK PATH FOR THE AMPLIFYING DEVICE, FILTER MEANS IN THE NEGATIVE FEEDBACK PATH ADAPTED TO PASS ALL FREQUENCIES OTHER THAN A PRESELECTED FREQUENCY, MEANS FOR SELECTIVELY CONNECTING BOTH THE POSITIVE AND NEGATIVE FEEDBACK PATHS TO THE AMPLIFYING DEVICE SUCH THAT THE SIGNAL IN THE NEGATVE FEEDBACK PATH WILL CANCEL THE EFFECT OF THE SIGNAL IN THE POSITIVE FEEDBACK PATH EXCEPT AT SAID PRESELECTED FREQUENCY WHEREBY OSCILLATIONS OF SAID PRESELECTED FREQUENCY WILL BE PRODUCED AT THE OUTPUT OF THE AMPLIFYING DEVICE, MEANS FOR SELECTIVELY CONNECTING THE NEGATIVE FEEDBACK PATH TO THE AMPLIFYING DEVICE WHILE DISCONNECTING THE POSITIVE FEEDBACK PATH THEREFROM SUCH THAT THE NEGATIVE FEEDBACK SIGNAL WILL ATTENUATE ALL SIGNALS APPLIED TO THE AMPLIFYING DEVICE OTHER THAN A SIGNAL HAVING SAID PRESELECTED FREQUENCY, MEANS FOR SELECTIVELY DISCONNECTING BOTH OF THE FEEDBACK PATHS FROM THE AMPLIFYING DEVICE, AND MEANS INCLUDING PHASE INDICATING MEANS, AND A DISPLACEMENT METER CONNECTED TO THE OUTPUT OF SAID SIGNAL AMPLIFYING DEVICE.