  We present the basic theory governing spin-exchange pumped NMR gyros. We
review the basic physics of spin-exchange collisions and relaxation as they
pertain to precision NMR. We present a simple model of operation as an NMR
oscillator and use it to analyze the dynamic response and noise properties of
the oscillator. We discuss the primary systematic errors (differential alkali
fields, quadrupole shifts, and offset drifts) that limit the bias stability,
and discuss methods to minimize them. We give with a brief overview of a
practical implementation and performance of an NMR gyro built by
Northrop-Grumman Corporation, and conclude with some comments about future
prospects.
