Power-recycled Michelson interferometer with resonant sideband extraction.

We present a system for the control and signal extraction of a power-recycled Michelson interferometer with resonant sideband extraction. This control system is capable of locking four degrees of freedom to a fixed point while locking the signal cavity to an arbitrary detuned point. One of the strengths of this system is that it can quickly change the instrument's frequency response without disrupting continuous operation. We report on an experimental implementation of this control system on a benchtop prototype and present broadband measurements of the prototype's frequency response for a range of signal cavity detunings.