report by Lil Squid from the Noun Project. See:

Le, T., Bhat, S. G., Subramanian, S. C., Waswa, P. M., & Redkar, S. (2019, August). Design and Analysis of an Auto-Parametrically Excited Platform for Active Vibration Control. In International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (Vol. 59261, p. V006T09A046). American Society of Mechanical Engineers.