A voltage controlled filter developed by Thomas Henry. Its most notable feature is that it produces eight signal outputs, at phase angle increments of 45 degrees. By combining these, it is possible to obtain 1- to 4-pole slopes. When the resonance is turned up enough to drive the filter into self-oscillation, it becomes a quadrature sine wave oscillator with 8 phase outputs.
The filter is named after the city where Henry resides, Mankato, Minnesota.