For most of the counties in MS, the so callsigns are just the opposite of JPD. The lower the number, the higher the ranking. Example: Lincoln County SO- Lincoln 01 is the Sheriff, whereas for a deputy, you might hear the callsign Lincoln-15. Your Constables are usually alway a "C" callsign- such as Lincoln C-05. Very High callsigns are usually assigned to Prisoner Transport Busses/Vans, such as Lincoln 50, and 3 digit callsigns are usually Coroner designations, such as Lincoln 360.
