report by Lil Squid from the Noun Project. See:

Fuente, J. D. L., Subramanian, S. C., Chinimilli, P. T., Redkar, S., & Sugar, T. (2019, August). The Design of Robust Phase Oscillator for Wearable Robotic Systems. In International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (Vol. 59230, p. V05AT07A058). American Society of Mechanical Engineers.