From The RadioReference Wiki
Within the past few years, numerous folks have devoted their time and energy to writing software applications that allow you to use your computer and scanner to decode trunked radio system control channels. Many of these applications are freely available from these pages for scanner listeners and hobbyists. They also allow Trunktracking for Motorola and EDACS trunked radio systems using a two scanner setup.
Please note! To implement these applications, a good bit of technical skill is required. You must have a good knowledge of electronics, computer systems, and trunked radio systems.