1. Introduction

2. Observations

3. Results
3.1. Line profiles
3.2. The 0.5 km s^-1 feature and absorption at 15 km s^-1
3.3. Rotational diagrams
3.4. Z x Z maps around IRc2

4. Analysis
4.1. LVG models of the SO lines
4.2. LTE models of the SO_2 lines
4.3. Isotopic and molecular abundances
4.4. Other sulfur-bearing molecules

5. Discussion
5.1. SO and SO_2 as tracers of shocks and hot gas
5.2. Nature of the 15 km s^-1 dip and 20.5 km s^-1 velocity component

6. Summary and Conclusions