  We present a scheme for locking optical cavities with arbitrary detuning many
line widths from resonance using an electro-optic modulator that can provide
arbitrary ratios of amplitude to phase modulation. We demonstrate our scheme on
a Fabry-Perot cavity, and show that a well-behaved linear error signal can be
obtained by demodulating the reflected light from a cavity that is detuned by
several line widths.
