Rotary INDUCTOSYN^TM is a kind of high accuracy angular position transducers and its high accuracy high-speed data processing circuit is an important part. In this paper, the different exciting and measuring modes of the INDUCTOSYN^TM are analyzed comparatively. The principle of absolute angular position measurement, the IRDC ICs and the error sources of the angle measuring circuit of the absolute INDUCTOSYN^TM are presented. Finally, the elementary study conclusions are given.