Balthazar van der Pol

Balthazar van der Pol (1889-1959) was a Dutch electrical engineer who initiated modern experimental dynamics in the laboratory.

Van der Pol investigated electrical circuits employing vacuum tubes and found that they have limit cycles. When these circuits are driven with a driving frequency near the frequency of the limit cycle, the resulting periodic motion becomes entrained at the driving frequency.

This behavior is similar to the behavior of the heart when driven by a pacemaker.